The 2.85s are for the "smaller" t-cases. These are basically the GenIs and the earlier GenIIs. The GenII 3.5s and 24V 3.0s (MT only?) have a bigger case/gears inside that allowed them to be able to cut a set at 3.15.

There are different gears between engines and MTs and ATs. You need to be sure to cross-ref to the mitsu factory gear that you'll be replacing when you order a set from AU.

Big Truck: 00, 3.5, Endeavor, 5-Spd drive line in hand!
Little Truck: 87, 2.6T I/C, MT, LSDs, Tonneau Top
Her Truck: 03, 3.8, 20th Anniv, 65k
Daughter's: 06 Eclipse, Keeping it Mitsu!
FSMs: MitsubishiLinks.com