Maybe I am a bit too late for this, but here are my thoughts:
Your truck has a beautiful patina on the outside, and patina happens only once... Why not embrace the way your truck looks, patina and rust? of course the floors need help, but why not keep its current finish as is visible from the outside? Re-do, de-rust anything hidden, to make it solid, but keep the outside the same: first, it looks very cool (maybe not to you and your wife, indeed...), and it saves work.You could chemically treat the rust from the inside, too, to stop it from spreading.
About the chassis, if you can afford it, have you looked into complete, "turn-key", aftermarket chassis? That is a nice, easy solution, even if expensive... You could modify your chassis for your need, with IFS, better rear suspension, better brakes... I am not sure an S10 chassis would be very happy if you go canyon-carving with 500 HP...
As for the engine, an LS engine is a great choice, there are also a lot of 6.0 litres around, bigger is better... One advice I have often seen is to mount the running gear stock, and only when everything fits and the truck runs well should you start modifying (turbo...).
As for running by spring... Well, maybe if you just deal with the mechanical part (stock engine, brakes, electrical...) and throw a bit of fiberglass on the floor, it is possible... And it would be cool, too!
OK, so I am not a purist like many members here, but we have to do what we can with what we have, don't we?
