The van/Hummer difference is all because of the turbo being center mount instead of side mount. No turbo back then so no reason to alter the headbolts or intake. The 6.2 used in hmmwvs were the same as the 6.2 in pickups except the bolt ons like starter, alternator, etc.
The oilpan is different than pickup ones, for 6.5 turbo and N/A, but I do not remember on 6.2.
The ffm on vans were different location, so the intake manifold might not have the 2 mounting tabs, look for that.