Gotta remember that there were a lot of us that were car/truck enthusiasts back in the 70's and 80's. We would buy an older truck or car and make conversions to suit our purpose. Back then, parts were easily available since most of these vehicles could be ordered either way. I've converted a couple of trucks and one car.
Fifteen, twenty years from now, some of you may be reading a post from some young guy asking if his 72 originally came with a 700 R4.
