I recently installed a set of oversize king pins and bushings in a 57 model (I think) 1/2 ton front axle.
This procedure works for the older trucks and likely newer ones as well.
Important to note that these 1/2 ton trucks came with fully floating king pin bushings, the bushings are a slip fit in the spindles and on the king pin, no pressing or reaming is required to install them. The down side is not only do the king pins and bushings wear as expected, but so do the spindles (the bores for the bushings). These spindles are harder and harder to find in good shape and not available new.
Compare this floating bushing design to that of all the larger trucks where the bushings are pressed solidly in the spindles and then reamed to size and in alignment, the spindles are then not a wear item.
I believe it is prudent to install the 1/2 ton bushings fixed in the spindles just the same as they're fixed in the larger trucks. Details to follow. No doubt there are other opinions on the matter, that's fine, this is my opinion.
The kingpin kit that is supposed to fit this axle is
NAPA 262-1432, standard size, comes with bronze thrust washer/bearing. There should be be other kits/part numbers that also fit.
This axle beam had oversize holes, elongated top and bottom in line with the axle.
The available oversize king pin kits for this application are limited. A month ago this was one of two in the entire NAPA system; let's hope they manufacturer more.
NAPA 262-6010 is 0.010" oversize on the kingpin diameter only, comes with ball thrust bearings.
I also choose this kit because I think ball thrust bearings are a better option than thrust washers in most cases.
I received the parts already disassembled, cleaned, and painted. First measured the bores in the axle and confirmed they were wallowed oversize and due for oversize pins. I also checked bores in the spindles and confirmed that they were not terribly worn, and thus still serviceable.
1. Order oversize king pin kit, NAPA 262-6010 as mentioned. (or a standard size if axle is OK)
2. Measure the bores in axle, measure the pin, and find your adjustable reamer to suit. (if installing oversize pins) PIC. Step 2
3. Ream the axle beam to just fit the new oversize pins. Only taking about 0.0010" at most per pass and might finish at 0.0002" per pass. Measure after each pass and adjust reamer carefully. (I like to ream left and right then adjust, less time than doing one side complete and then the other.) Ream carefully so hole is straight and smooth without chatter. Oil and test fit the pins to be sure they can be tapped into place, the loosest you'd want is a firm push with the palm of your hand, and no tighter than several gentle whacks with a soft hammer. If the bore is even 0.0005" over pin diameter it'll about fall through. (Reaming only if installing oversize pins) PIC. Step 3
3.5 test fit the lock pins in the axle, clean, debur, file, or ream the hole just enough so they fit freely.
4. Prep the spindles. With a custom ground punch work the previously peened divots back to their normal diameter so new caps/plugs can be fit later. Also scrape and wipe any paint and grease out of the bores and from inner surfaces of spindle (where it fits over end of axle), paint thinner works well. Use a file to remove any burrs or wear ridges also present on the inner surfaces. May also need to use a pipe tap to clean threads, do not cut any more than just the paint/crud. PIC. Step 4
4.5 Prep the axle, remove any paint and with a file remove any burrs from top and bottom surfaces.
5. Wipe any grease or oil off the new bushings and test fit them in the spindles and be sure you can line up the grease hole with the grease fitting hole.
***Next is a modification from original practice to prevent wearing out spindles***
Using Loctite 660 or a similarly suitable retaining/filling compound smear a good coat on the outside of the bushings and slip them in the spindle bores, line up the grease holes and make the bushings just flush or a hair below the inside surface of the spindles. Wipe up any extra. PIC. Step 5
6. Slide the pins in the bushings and wait a day or more for the retaining compound to set. This step is very important if your spindle bores were worn much. This ensures that the king pin will fit and that the bushings (already made to size) share the same center line. (Reaming later to fit the pin is not an option unless somehow you get or make undersized bushings..) PIC. Step 6
6.5 test fit your spindle and the thrust bearing over the axle, fit any shims necessary to take up the gap on the top side
of the axle. Don't pound and wedge it together but also don't leave any gap a shim will fit in. (in my case no shims were necessary but before it would fit together nice and snug I had to remove the burs and wear ridges as previously mentioned.)
7. Grease the thrust bearing, pack it full. Also apply Anit-Seize to the kingpin and lock pin bores in the axle. PIC. Step 7
8. Grease the inside of the bushings and fit it all together paying particular attention to lining up the flat on the pin with the lock pin hole in the axle. If it is not just right the pin won't fit. Then fit the pin, figure out if they go front to back or back to front as might be necessary to bolt on a steering stop bracket. ***Very important to drive the pin in solid with a hammer and large punch*** The lock pins are very soft steel and not intended to be drawn in with the nut. Instead the nut just keeps it from falling out later, that's all. PIC. Step 8
9. Fit the caps/welch plugs by first seating them with a socket or pipe that fits the outer diameter. PIC. Step 9
10. Use the mostly flat side of a hammer to flatten
the plug. Flatten because this causes the diameter to increase and fit snug in the hole, if you fully invert the plug it'll be about as loose as when you started. PIC. Step 10
11. With a punch stake the bore around the plugs in about 4 places. Without doing this it is possible the grease pressure (when greasing) can pop the plugs out. PIC. Step 11
12. Don't forget to fit any steering stop bracket on the lock pin and just gently snug the nut on those weak/soft pins. Fit new grease fittings and grease it.
Admire your work! PIC. Step 12