You're in luck dude... i have a dissasembled mx13 diff sittin in the backyard. The bearing OD is 72mm. The width of the axle shaft at the bearing is 35mm. Bolt spacing is about 80x45mm. It's not actually a perfect square so your measurements are probably correct as well. There's too many mozzies to go out again. If you like i'll measure them properly tomorrow.
Eddie.
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