Originally I think there was a difference, more to do about harden tips injectors and IP internal parts, then about flow rates. The '84-'87 CUCV use the long injector with the fine treads
However there were at least 2 different IP pumps model #' for the CUCV series(?) if I remember correctly, but I am not sure of the difference as other treads appearer to use effectively what ever 12v. IP is available for '84-'87 " J" code engines.
the post was in Diesel place, the harden parts are for with standing the thiner artic fuel mix and dirty fuel sources