wOw ... flashback!
I had a '68 GMC with similar roots ... it'd been used for farm work for many years before I picked it up, and certainly looked it. I got a couple good seasons out of it before the six banger blew up, but fortunately, a kid across the road totalled his Roadrunner about the same time.
?
I got the drive train for next to nothing and wedged that into the truck. Cut the Mopar mounts out of the car and just dropped the motor in, welding it to the truck frame. A Custom by Cobble trannie mount, and cut and welded both driveshafts together. Would you believe it ran great, and even smooth, at highway speeds? With a couple cords of wood in the back? <G>
Kind of a FrankenMobile once the dust settled. I also tore out the stock bench seat and put in the buckets and console from a Bronco, completing the full G M C crossover. G for GM, M for Motocraft, and C for Chrysler ...
Finally lost it when one of the front end king pins broke ... wheel went sideways in the fender, resulting in what some would call a "significant" loss of control. I left a pretty good dent in the inside of the driver's door ... those metal panels are HARD, but not as hard as me! :-}
The moral there ... DO check that front end out closely ... not something you want to ignore if it's got miles on it.