Okay, don't judge me too harshly by this question. but, would it be possilbe do you think , to make up some chunky washers, 2mm thick. And use those to stand off an H150 head, in a 145 housing? and then run around the periphery of the diff head with a caulking gun, filling up the gap with some high grade sealer? Or does the rear axel assembly rely on having full surface area contact for strength? (I know that the diff housings are pretty flimsy) The reason I ask is I can use a lathe anytime(to make spacer washers), but making a spacer shim requires a bit more presion and care.
Also I know a bloke who has a 3.7:1 diff head.

I also reckon that this thread has some good info worthy of the tech section.