It is not the housing that changes for 2.45 gears, only the carrier.
My '75 housing came factory with 2.45 gears and open diff carrier. I installed a late model Trac-Loc with 3.55 gears, no problem.
BTW - Don't waste your money on the side bearing adjustment tool ($100).
Go to the hardware store, and for $15 you can get a length of pipe and two large huts that will fit the adjusters perfectly. I used a 36" length of pipe, because the tool works the same for 8.25 AND 9.25 axles.