Ford vans are easy to lift Quigley or not. Look to U-Joint or google for answers.
As for Chevys, not sure but I believe they have been lifted too. Again, google.
I have an '02 E450 short bus with U-Joint 6 inch lift and 4X4 conversion. Was 4X2 when I purchased it.
Weldtec in San Diego has Chevy Van lift kits that work with the Quigley 4x4
What year is it? I used reindexed torsion keys for the front of mine and rear blocks can be had from Weldtec as has been mentioned or directly from Quigley. Turned out the keys that fit were from the latest model Hummer H2. Quigley will provide GM part numbers if you give them the VIN. I achieved about 3 inches of lift and am running 285x70x17 tires.
Should be mentioned mine is a 3500 so again check with Quigley for GM parts but I’d bet the same approach would work.
Hmmm, they can't even supply the build sheet? They may not have parts for it still, but they could, I think, provide you with the build sheet so you could get part numbers and then decide what you needed to order from other places.