No differences
Manufacturer was the same with the 3 names you listed. Just had different names. Went from Kaiser-Jeep ('60's) to General Products Division(1970-1971) to American General (1971 on).
In the early '60's on down to the '50' there were other manuf as well.
Now as the years progressed with the truck, many updates were introduced including the engine LD->LDT. I have seen a handful of LD engines still kicking around. The transfer case was also updated from the Sprag to the airshift. However, there are many deuces out there with sprag units. Also, in 1987-1988 the split circuit brake system was employed in these later year trucks.