The big block will require some work, but it is do-able. You will have to go with heavier springs. Close fit headers are needed.
The small block is a better fit, and with the right setup will make a good driver, with better economy. My 69 has a very torky 350, th400 and 307 gears, and makes a good daily driver. I can do burnouts, but nothing like what a big block will do. It all boils down to what you want out of your truck.
Plans for my 52 include a 292, th700r4, and 4.10 gears. It's a 3/4 ton, and will still be a work truck when I finish it.
