What model/brand transfer case do I use? Are transfer cases interchangeable?

You'll need to obtain the proper correct direct replacement for the vehicle. No one here in this forum will know the differences between the models you've shared; but a good rule of thumb is: whatever came with the vehicle is what should be used. There's no substitutions possible. Check a local salvage yard or a used parts network like LKQ or even on eBay to find the part you are seeking if a GM dealership is of no assistance. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops