HD's are all 3.29 diffs. The 2.93 is created by using a 33/37 drive/driven gear/chain setup at the other end of the trans with a 3.29 ratio diff. When you divide 3.29 ratio by the chainset 1.12 you get 2.93.

GM calls the diff the final drive which I originally found confusing. I was thinking final drive ratio was the overall ratio. It isn't.