This is a popular swap because you end up with modern brakes and steering, and a more modern drivetrain with better highway gearing. If you go to a V8 (or V6 for that matter) you will have to play games with your steering column to get it out of the way of the engine so you might as well find a tilt wheel column too. (You can cut off the original and weld a knuckle on, then fabricate a piece to the steering box.)
The S10 frame is a good one. I have also heard about some cars like the mid '80s Monte Carlo. All you really need to do is measure the track width (measurement from front tire to front tire) and the wheelbase and try to find something the same. It's a lot easier to shorten or lengthen the wheelbase than to change the width of a frame.
No matter what frame you choose you will end up fabricating the body mounts. You will also need whatever electronics go with the engine and trans if you don't plan to throw away the fuel injection and electronic ignition and go back to a carburetor and old style distributor. (Some of the newer transmissions won't work correctly without their electronics...)
It is best to get the whole vehicle that you are cannibalizing for parts. Then you can pull off all the components you need, even down to the wiring harness.
Don't expect to get this done in a weekend. Working full time and just tearing down and reassembling would take a pro working alone and with all the right tools a month or so. Once you get it apart you will find a million things you want to clean up, sandblast, repaint, undercoat, replace, etc.
I need to do this for mine but I love driving it so much I keep fixing the nickles and dimes while I gather up parts and make my plans for the big swapover. I have had my parts truck for about 6 months now and have been planning what to do and how to do it for a couple of years.
Best advice is, spend a lot of time reading these forums!
