I'm doing this on mine but reaming the balljoint holes on the GMT800 knuckle to the bigger GMT400 balljoint size so I can keep stock lower control arm.
If the GMT800 lower control arm is longer/shorter that's probably the problem.
You can buy offest bushings for the upper control arm for cheap at Rockauto that should give you a little bit of leeway on camber.
How bad is it now? And in what direction?
This is not a super uncommon swap to get the better two piston GMT800 Calipers and discs that slip over the hub bearing units onto GMT400 HD trucks (which have rotors pinned to the back of the hub flange with the studs from behind, and only single piston calipers with smaller brake pads and much less swept area).
I'm using outer tie rod ends from a 2wd C10 that I reamed my spindles to fit. They fit the stock GMT400 adjuster sleeve (it's a common size for older GM vehicles, 11/16" iirc).
If the GMT800 lower control arm is longer/shorter that's probably the problem.
You can buy offest bushings for the upper control arm for cheap at Rockauto that should give you a little bit of leeway on camber.
How bad is it now? And in what direction?
This is not a super uncommon swap to get the better two piston GMT800 Calipers and discs that slip over the hub bearing units onto GMT400 HD trucks (which have rotors pinned to the back of the hub flange with the studs from behind, and only single piston calipers with smaller brake pads and much less swept area).
I'm using outer tie rod ends from a 2wd C10 that I reamed my spindles to fit. They fit the stock GMT400 adjuster sleeve (it's a common size for older GM vehicles, 11/16" iirc).