It would be nice to restore to stock, but I can understand that your son might be looking to hop it up. What teenager didn't?
A latter day frame driveline often used is from an early Chevy
S10. It's not a totally simple swap, but is one of the easiest. If your high school has shop training it could be a good project and lessen the cost. Here's a link for you and your son to look over before making a decision.

http://www.chevytrucks.org/tech/s10_frame_swap.htm

As typical of your Southwest area, the body looks to be in very good condition.

Drew