Quite possibly! Its an old 1.5ton gmc, though i think the weight of that engine would crush the front end of the truck. :) actually he’s been trying to find a 6.2 liter diesel to replace the one that cracked the main bearings but they ALL seem to have that issue
Try one from a junkyard and measure the clearances to determine if the main bearings are cracked or need to be replaced. I assume the main bearings is the crankshaft? So try the crankshaft first rather than replacing the whole engine
No the main bearing journals for the crankshaft are notoriously weak on the 6.2. You can actually feel the cracks! Just do the oil pan and rub your fingers along the main bearing journals and you can feel the cracks