Not all 900 series cars have independant rears. I kept the gear assembly when I had to scrap my wrecked while parked '92 940 Turbo (auto)--but like yours, I think it's a 3.73. There may be another option for you other than finding another locking rear with a different ratio---but I don't know for sure if this will work for the 700/900 series. I just completed a job on my '69 144S which I use for a few track days each year. It had the original 4.10 rear (early 140's - expensive to rebuild). I found a '73 140 rear (later 140/240 rear parts much more reasonable) with 4.30 gears. I disassembled that later rear and added a used limited slip I'd saved from a 265. This same procedure may work for you--find another rear with the ratio you want. Replace the axle bearings and seals and add the locker to the diff. You won't have to touch the pinion gear and the side shims will 99% remain the same as original even if you replace the center carrier bearings.