hey 8t8, welcome to the garage! if your truck originally had a V8 then it will have 2 things: a VIN starting w/ a "V", and the front mounts on pads rivetted to the front cross member - if the current V8 has the side mounts on an add-on cross member then it's a later V8 [like 350]
original V8 would have been a 283, great engine, and my preference for real traveling, but the 235 is good too, just less power -
red= 283, green= 235 as said, watch the swap section here, and e-bay if you deal with them, and any local buy-n-sell papers in your area as well as auto swap meets, there's lots of 235's around
Bill