Ford 8.8 Swap
41 is a 3.27 open, D1 is a 3.27 posi.
the 3.27 is an oddball in the 95+ disc rears, but common in the boxy drum-braked 91-94 explorers. want discs and a 3.27? easy....just take the housing from a 3.27 91-94, and pull all the axles and brake stuff out of a 95 and put it in there. any junkyard will have all that stuff at any given time.
3.73 posi (D4) is by far the most common in an explorer.
4.10 posi (D2) isnt rare, but nowhere near as common as the 3.73
for whatever reason, Ford made it impossible to get a 3.55 posi in an explorer. you could get a 3.55 open, but not a posi. But just because Ford said you couldnt order it doesnt mean theres not a few out there. Something always sneaks out the factory doors. They also said a 3.08 posi wasnt available in an F150, but I found one for my truck once...