Frame swap ’47 panel truck with ’88 k2500. I’ve had the panel truck for almost 30 years and daily driver for 10. I started this build Two years ago, so I’ll post alittle build history each week until I’m caught up to real time progress.
I farmed out the heavy lifting and now work on what I can. Before I get too far will it work? Here is what I mocked up.
The wheelbase is the first thing I considered when determining a donor frame. The 1947.2 wheelbase is 137". The 1988 K2500 single cab long bed wheelbase is 131.5". The frame width is going to have to work. ’47 1 ton is about 35", the ’88 K2500 is 45". There needs to be 5" of clearance outside of the ’47 frame for this to work.
There is about 10" between the frame and running board.
The ’88 frame drops 8" under the cab. The ’47 battery tray will need to be trimmed. I’ll replace the battery tray with a box for storage or electronics.
I was concerned with ride height, so I measured from the top of the frame to the bottom of the springs. The ’47 is 10", the ’88 is 13". If I place the ’47 body on the ’88 frame, the relative position of the wheel to the wheel well will be 3" greater than the stock ’47.
The ’47 has 2" wood mounting blocks. There are rails across the bed underside. The bed can be mounted closer to the frame by removing the wood blocks and modifying the rails. It looks like I can set the ’47 body on the ’88 frame and maintain the stock ’47 stance.
I have LT245/75R16 tires on the rear currently. Those are about 30" tall. If I maintain this stance, the space between the top of the rear tire and the fender will be 4". The fender opening is 31" so I won’t run a taller tire without modification.
This rear end is from an ’86 suburban. I chose rims for clearance of the tie rod ends, so ~4" back spacing. There is some room to move the wheels in with greater back spacing. I’ll get exact measurements for that. I planned on keeping the 8 lug rear axle, and modifying the front of the donor rig to 8 lug.
The rear tires are 74" wide and the front tires are 63" wide on the ’47.
The ’88 tires are 71". This will move the tires out 3.5" on the ’47. With an adjustment to the wheel back spacing, the tires should fit inside the fender.
Two years ago (9/2019) I drove my panel truck for the last time, as it was, to the resto shop. A week later I drove the ’88 GMC there, the panel truck was being dismantled and they hit me with a healthy bill. One of the stipulations of the contract is that we meet once a week to go over progress, keep motivated, and settle up the bill. Each week I visited the shop, a little progress being made. They stripped both trucks down faster than I could have. The body was on a cart, and the two frames were side by side. Comparing body mounting points and deciding how to modify the donor frame. The ’47 gas filler is on the passenger side. 1988 the filler is on the driver side, tank is inside the frame rail. Pre ’88 the tanks were outside the frame and an auxilliary tank could be added to the passenger side. That doesn’t appear to be an option here, the ’88 auxiliary tank was behind the axle and I want the spare tire there. It could be done, re-route the exhaust to the driver side and find a tank with the passenger side filler. There is the driver side transfer case, so exhaust would go below that. I decided to go with moving the filler to the driver side on the panel. We used the brackets and frame ends from the ’47 frame. The original frame had extensions on the rear. We decided a frame bracket template would be a good way to locate the body mount brackets. With the Z-axis points determined, I want the body to ride at or near stock height, so the 2” wood blocks won’t be used. The 2” hat channel cross sills will be replaced with 1x2 tubing layed flat. This will put the bed as close as possible to the frame. All other mounting points are lowered about 3” relative to the bed mounts. Now all the brackets can be tacked in place, and the body will be test fit.
12/2019 The ends of the ’47 frame were cut and grafted to the donor frame. The rear frame extension is offset lower for two reasons. The body will be closer to the frame so the rear bumper will be lower relative to the frame, and there is a rear cross sill attached to the body that mounts on top of the frame. The rear end was moved back. The front frame ends are narrower on the ‘47, They tried to use them, but decided to just fabricate something. The plan was to measure everything again and bolt the rear in place. With the rear bolted in, roll it over to the alignment shop. After it’s dialed in, the rear hangers can be welded. I decided to leave the six bolt lugs for now. The 8 lug rear from the ’86 suburban is narrower between backing plates. I don’t know how the wheel mounting surface to wms compares to the ’88 6 lug. The 8 lug rear could fit with some modification. This can be done later, as the focus has shifted to the best use of funds to keep the project moving. The body mounts are tacked in place and the engine is back on the frame.. A few bed boards are being used to locate the new 1” cross sills(1x2 tube). Next step is to mock up the body on the frame.
The body is on the donor frame, (it has a 2x4 under the front in the picture), still needs some adjustments. The bottom of the firewall above the transmission will be modified. The rear of the rear inner wheel well will be trimmed to accommodate the leaf spring. The 1x2 cross sills have the bed as low as it can go without major mods. The next step is to hang the fenders, start carving the front inner fenders, and locate the running board brackets. The front and rear running board brackets have conflicts, so will need to be moved. The radiator will need to negotiate it’s placement based on the location of the steering gear. It was a good feeling to see the body on the frame, this is a good milestone in the build. There is still a long way to go, but this is a positive turn.
The rear fenders are set in place, and the runningboard brackets placement are being located. You can see where the Mr. Peanut was removed from the side, and the 5¢ on the door. The rear tire is inside the fender, I’m curious how the front tire will be. The rear wheel might could be moved ½” forward to center in the wheelwell. I didn’t measure, but it looks like the distance from the top of the tire to the wheelwell is close to the 4” = stock height. In my preliminary plans I figured the stock height could be preserved if we removed the 2” wood blocks, and replaced the 2+” hat channel cross sills with 1x2 tube. After teardown and using the body/frame template, we thought it would have a 2” lift. Now that it’s coming together, things are lining up well. There is plenty of clearance between firewall and engine. The firewall had to be modified just above the transmission, but not much. Next steps are to attach the runningboard brackets, modify the front inner fenders. Once the front fenders are in place, the core support will be addressed.
I like how the front tires don’t stick out of the fenders, they are just inside. I may be able to run wheels with a greater positive offset to suck the tires in. The fan and fan clutch are being greedy in the core support area. The plan was to get the grill and support panel mocked up and see how a radiator will fit.
Things continued moving along. The front sheet metal is being fitted. Time to get everything mocked up, so I delivered some parts last week. Awhile ago I picked up a new GM steering column from someone who gave up on a jeep project.
While I was looking for similar builds, I saw on a build that used a Kugel Komponents Brake bracket. I called them and ordered separate Brake and Clutch brackets since they didn’t offer a separate clutch bracket. I need the clearance for the stock brake booster. Ordered on Tuesday, arrived on Thursday, Wow! I also went to the parts yard and cut a fuel filler door panel out of a Nissan, that was fun…
While all the heavy lifting was being done at the shop, I was busy back at the bench figuring how to run the original speedometer from the electronic signal of the newer transmission.
The grill being fitted. I got some seats from a Chevy Caravan. Mocking up the steering column, pedals, and seat. The steering column is in as well as the Brake and Clutch assemblies. They used a section from the donor steering column to join the GM column to the donor shaft, needed about 7”. We also took the hole from the donor firewall. The pedal assemblies are in place. Still need to put in the donor gas pedal, and the foot starter bracket. The gas tank has been repositioned a little forward and a little down for clearance issues. The fuel filler door is in place. It looks like the battery will sit under the passenger seat. The original location was under the passenger floor, but with the wider frame that won’t work. There is an access cover under the seat, the battery can be lowered in and rotated to sit towards the outside. The exhaust runs through that area, but there’s enough room for a battery. The other option is to have the battery high on the inner fender, under the seat is a cleaner option.
6/2020 The fuel filler door, looks like they had a **** of a time with that. It is what it is. We now have a bracket for the parking brake lever. Still working on the bracket for the foot starter linkage. The foot starter linkage will not include the arm that attached to the starter. It will just be the foot pedal and the curved bracket that it is attached to, and will mount on the body to actuate a momentary button. The plan is to have that done by next week and remove the body from the chassis to finish the welds on the body mount brackets.
I have been working on the radiator issue. The steering gear interferes now, and I am running the stock ’88 fan and fan clutch. I looked at using the original radiator shifted up or out at the bottom, there just isn’t room to go up much. I looked at using the ’88 radiator, I even tried a ’70 camaro radiator for fit as I read that might work. There are brackets behind the front grill that restrict that area. I drew up some plans and went to the radiator shop for feedback. They suggested I go with a modified downflow, mock it up in cardboard for fit. So that is what I did. My builder changed the core support bracket to accommodate a radiator. I drew up some final plans and am ready to go back to the radiator shop to have a custom radiator made. I will use the stock ‘50’s top tank (20”) and have the bottom tank cut down to just under 18”. There is a band on each side of the core, so the max width will be 18” with the core just under that. 25” tall with the frame and core support being different from stock there is room to go lower. We’ll use 2-row dimpled core, so I’m hoping it will be thin enough to not have to cut into the latch panel much. The top tank will be offset to the rear. I had been running a 235 inline six with the stock radiator mounted to the front of the core support, so there is about a 1 ½” cut out in the latch panel. The radiator should look right when in place. I’ll ask if we can fit in an oil cooler in the 2”x 18” gap.
