Don,
Which route you want to go depends on a lot of factors. What is your final goal? Is all you have a cab at this point?
If your goal is to build a street rod that drives like a modern truck with IFS, Disc brakes, a V-Motor and auto trans. I recommend the S-10 route. I resell a kit that a buddie of mine in MN designed and builds. We include the pieces in the kit to take a complete S-10 Chassis (82-04) Strip it down, attach the body mount kit, then set the body on. Our kit also includes pieces to reuse the S-10 Brake components, Steering Column, Brake pedal, Gas pedal, and Wiring harness. The kit also includes motor mounts for the V8, 4.3 V6 or early inline six and a transmission cross member for 700R4 or Std. A.T., or TH 400.
To address the bed depth issue that Scott mentioned our 2 inch drop kit actually drops the cab, running boards, and front clip down 2 inches but leaves the bed setting on top of the frame rails, we include a filler panel in the kit that fills the gap that is created between the splash pan and the bedside in front of the rear fenders and the rear fenders are dropped 2 inches lower on the bedsides. It also adds to the hot rod look of the truck as the rear of the bed sets higher on the back of the cab, it's a different look.
We've had trucks with a Rustang 2 (Pinto 2) and the F*rd parts always bothered me, A Camero sub that I liked but never drove enough to build a firm opinion on, and a late 70's early 80 sub that rode great but had the wide track issue that looked funny to me. I drove S-10's for years and always like the way they drove.
Your on the right track getting various opinions before you get started, keep in mind that your looking at a lot of work with any solution even ours. Especially considering your starting with just a cab. Like Scott said if you like to tinker and have done fabrication work before the S-10 swap can be done yourself, the benefit of the kit is we've done the tinkering and smoothed out the rough spots ahead of time for you. I always recommend before you spend any money on any solution get going on your body work and in your case get anything that needs fixed on your cab done first, corners, cowl, etc. So many guys buy all kinds of parts and then get into the body work and realize the work required to do the body work and that they don't have time/knowledge to do it. Then get mired in that and don't move forward.
We've also done several complete chassis for customer including runners shipped to their door. I've also always got a couple stock chassis setting around from customers moving to S-10's as well if you decide to go the stock frame/sub route. If you go that route you may want to look in your local area for a complete donor truck to save on shipping.
Don't get me wrong, I love the old trucks in all their forms, bone stock, mild custom to full bore street rods. I've got a bad habit for big trucks too. I'm just happy to see them on the road however they get there.
Steve