correct on the axles, your statement about cummins and allison being the same company is incorrect though. gm was using aam axles since 1973 in the trucks/suv's, when the 12 bolt and 10.5" 14 bolt ff started being used. in 1980-81 the 10 bolt front and rear axle started its production (excluding cars because i dont know when gm started using aam axles in the cars) and the 9.5" 14 bolt sf appeared around 1984 in the 3/4 ton trucks and the "heavy half ton" trucks, only rear axle offered as both a 6 and 8 lug variant. in 2000 when gm switched body styles and introduced the duramax and the 8.1L vortec motors the 11.5" 14 bolt ff was introduced.
for front axles the dana 60 was used until 92 in the 1 ton application, when the body was switched. you will find 1 tons in both the 73-91 and the 88-2000 body style trucks, the 73-91 version was solid axle front and rear whereas the 88-2000 models were IFS and solid rear. odd that gm offered both body styles for 3 years but both were available.
