He said he bought them TO part out... How can he sell them for parts when they are already stripped?
Try the local PD. OR if your town ever has one of those gun buyback programs, go CASH IN!
Finally, you can look up DEMIL procedures... The ATF says the receiver has to be torch cut in (3?) places. The army uses a machine that chews them up like bubblegum. I think a chop saw would suffice myself... Who wants to bother welding junk back together? Whatever you do, DON'T just chuck them whole... They could be found in the trash, and that could be a problem for you.