Chad, go to my Hub Garage and you can see lots of pics of this GMC (click pic for large images).
http://www.hubgarage.com/mygarage/6dee7
GMC is sold but I kept the wheels for my current 72 Cheyenne Super clone project.
GMC was dropped 5"/7" it's bagged in the front w/dropped spindles and dropped leafs w/shackles & helper bags in the rear. Truck had c-notch and a shortened 9" in the rear.
TT2's are;
Front 17" x 9" (9.5" outside lip to lip width) w/4" bs
Rear 20" x 10.5" (11" outside lip to lip width) w/4" bs
Tires in the pics are Falken GRB FX-451 255/40ZR17 & 285/30ZR20.
Replaced later with BFG KDW (flame gruve pattern looks kool) 255/40ZR-17 & 295/45R-20 is what I am running now. Gave it more of a biggy & little raked look. Hated the rubber band look on the rear with the Falkens.
FYI-My stock 72 12 bolt is too wide to tuck these wheels with that bs. I picked up an earlier, narrower 12 bolt from a 67-68 that will put me closer (.75 per side) but before I buy axel’s I need to mock it up to see if it needs to be shortened.