Patrick66,
GREAT to hear you're sharing your interests with your son!
Personally, I believe you'll be helping him build his character and learn to work towards guidelines and goals to finish a project. Plus, you'll be keeping him at home and away from all the trouble kids today can find out there.
Now, on to your chassis question. First, the S-10 might seem like a close match. However, as mentioned above, the S-truck chassis has a very unusual shape to it, in that looking at it from the side, you can see that the frame rails "dip down" in the middle for the cab to sit lower to the ground. Also, the steering and front frame rail configuration WILL make life difficult for radiator/front sheetmetal/front bumper mounting. This being said, several individuals have done or are doing this swap under the newer Advance Design pickup. Check over in the "Hi-Po Shop forum for some good links to online information.
As for the GM midsize car (El Camino) chassis, two words-
FORGET IT! It is totally the wrong shape to fit under your truck. The GM midsize chassis is what's called a "perimeter frame" design, where the frame rails in between the front and rear axles spread out to the full width of the car and run along the inside of the rocker panels. In other words, were you to put your truck on one of these, your frame rails would be sitting under the outside edge of your running boards.
Probably the best option of all would be the tried and true upgraded (Mustang II) crossmember and rear leaf spring suspension on your stock chassis. Just go over it carefully to check that it's in good condition. Hope this helps.
Regards,
Wannabe
