I bought this '91 GMC Suburban, along with a donor 89 Chevy Suburban back in 2020. It's be a ton of fun and I've been slowly upgrading it along the way.
So far I've:
Replaced every fluid in the rig.
Replaced the steering components with beefier components.
Added a 3" suspension lift in front, 3" blocks in back, and new shocks all around.
Upgraded to 33" tires, adding some minor clearance with the help of a careful sledge hammer work and a few particularly rough trails.
Added a 484 big block TBI with a 1" riser and a bowl filter mount (TBI & Riser came from the Donor rig).
Replaced the front auto-lockers with manual hubs.
A bunch more small things that I am not currently remembering.
What's Next: (In order of preferred priority)
Fully rebuilding front and rear diff, installing limited slip in the rear and a good old lincoln locker in the front, along with a lower gear... moving from 4.10 to 4.56.
PAINT!!!
Rebuilding the donor engine & installing
Install nerf bars (harvested from the donor)
Building & installing a custom roof rack
Rebuilding the donor transmission & transfer case & installing