G'day Jason,
HQ/HZ stubs will assembly straight onto a HR ball joint front end. Technically this will give you a slight bump steer problem because there is a 15mm height difference of the steering arm bolt holes. Also if you use these stubs they will lower your car about 15mm.
I know Hadfield make a 2inch drop stub axle to suit HR front which will accept the commodore brakes, or you can use Hadfield modifed drum brake stubs which don't lower the car but accept the commodore brakes. I think from memory the drop stubs are about $450 the pair and the drum brake stubs are $250 c/o.
Just keep in mind if you intend to drop the van on its guts you might be better off with drop stub axles as you still need to retain 3/4 of the cars suspension travel to make it legal, but check this with your states road authority as each states different.
Regards
air-chief