I agree with Mike on the use of the S10 frame, but there are a lot of guys out there doing it. The answer to your question is "Yes", the SBC and TH350 will drop into the S10 chassis without problem.

I looked at a very slick '40 Ford pickup several years back, and the guy had it priced pretty low, in my mind. Then he shared that it was sitting on a S10 chassis with all S10 running gear, which meant it was not a '40 Ford, but a gennie steel PU body grafted to a modern frame. He was finding that the value of the combined vehicle was a small percentage of a gennie/repro frame based truck.

That said, it's your project and it only has to make you happy. At least you're keeping it all Chevy, but be aware of your potential for resale as you make your plans.