The front of your S-10 is probably the correct width. A two-wheel-drive rear is narrow under your truck. The rear from a four-wheel-drive is supposed to be wider, and should fit better. If your S-10 is an extended cab the wheel base is too long. But if it isn't, it is too short... They are supposed to be easy to shorten.

The Nova subframe swap is commonly done, and should work reasonably well.

Check the newstands. One of the truck magazines has an article about putting the S-10 under a truck like yours. Tex Smiths book on Hot Rod Chassis has a chapter where they describe putting a GM G-body subframe under one of these trucks. I'm planning to follow that book to do my '54. I have the frame donor stripped and sitting in the yard right now.

This is my first post here, I hope its helpful!