First car? 1980 Checker Marathon with a Olds 350 Diesel and a Turbo 400 trans.

I turned it up quite a bit. I was going to GM's engineering school at the time (GMI in Flint, MI)

30mpg with 8 guys in it. Not super fast but torque fir days.

First truck was a 63 GMC 1/2 ton with a 305 V6 (GMCs didn't run chevy engines then) with a Powerglide.

Also had a truck that started out as 2 82 F-150s spliced together, rotted rear frame on one, frontal collision on the other, cut and spliced the frames. Then I got a 79 bronco with a rotted body that I put the 82 cab and nose on, and cut the bed down to 5 feet.
400 V8, C6 trans, NP205 T case, 9 inch with a locker, dana 44 posi in the front. It would go anywhere. At 5mpg.