75 valiant build, go back stock /6 or v8

Okay. New idea possibility for this build. My son and I were kicking around engine idea builds for it. As he is normally the one wanting to stay clean and original with the cars. He said, surprisingly v8. Then half jokingly said what about a hemi. Of course I don't have the budget for a 426, don't want to deal with the new computer driven ones. Then I remembered a buddy selling a '56 firedome desoto with a 331 hemi in it. He wants like $500 for the whole car. Could probably get it cheaper as he hires my son and dad to do work for him transporting hay equipment and tractors around the valley. I know not as straightforward as a Schumacher v8 conversion, but dang the cool factor.