Take a look at my photobucket, I'm not sure if you have yet.
When I was looking for a frame I put an ad on Kijiji (what we use instead of Craigslist) and I had my pick of frames. It might be worth it for you to try that.
If the work done to the frame is good, then you can definitely start with an already bagged truck. Mounting these cabs to the S-10 frame is a little tricky just at the front of the cab (the frame widens and the cab narrows), but I was able to get around this easily, although it does limit how low the truck can be on the frame.
Yes, you can use all the steering parts. I think I've mentioned this to you already, but in addition to the frame and stock rear end, I used the brake booster and pedal, steering column, steering shaft, seat, emergency brake pedal and cables, gas pedal, gas tank, filler neck, steering column/booster brace (under dash), etc. from the S-10. I had a stripped frame as well as a complete 92 parts truck so I got all the parts I needed. I really think this is the way to do it, especially as far as the brakes, since everything is meant to work together.
No, you don't need a different rear end. It's a huge misconception that because these are light-duty trucks that they were built light. My dad's '52 1/2 ton has a 454 with over 20,000 KM's on the s-10 rear end and it holds up just fine. I've got the stock rear end in my '46 with a 455 Buick as well.
You can make a choice though since you're planning on using 2" wider fenders. I used the stock rear end, with 15x10" rear wheels with 3-3/4" Backspacing and 31x10.5 15 Tires, but I tubbed the box. With that spacing they fill the fenders just right. If you're going with the wider fenders you can either go with a wider wheel, or you can go with a 4WD S-10 rear diff which is either 3 or 4" wider, so about 2" per side. I like the deep dish wheel look so that helped my decision, you can decide what you want to do. However, if you do switch diffs, keep note that some of the 4WD Blazers had rear disc brakes. If you go that route, you need to change your master cylinder as well. Just make sure whatever rear brakes you use that the master is matched.
Just an extra note, my body is mounted about 4" off the frame, and I lowered the frame 2" in front with spindles and 2" in back with blocks. I originally had taller blocks in the back but had to put shorter ones in for the right stance and more clearance. My front wheels are 15x8" with 3.5" backspace, and my front tires are I think 225/60R15. That should give you an idea of tire heights and such. The style of these bodies and the differential height of the running boards at the back of the front fenders compared to the bottom of the front grille pan make it hard to get them really low for ride height, and as well because I tubbed my box and used such tall tires, the curve of the fender where it meets the box side limited my rear ride height. It ended up exactly as I want it, but these are things for you to keep in mind.
I hope that helps.
