Im hearing that Dana has Axels you can order in a create , so with that being said they might have the parts to do disc brakes possibly
If you find a D80 with disks it will be a 3. 55 and then your front will still be a 3. 54.
However, I am told after much research and speaking with many companies that you would not have enough guts in the 1st gen brake booster for it to work. Would also new the hydra boost system off a second gen then.