we just used the front and rear hubs of an R33 GTSt to do a 5 stud conversion on a ceffy. We also swapped the RB25DET, gearbox, wiring loom, ECU, power steering pump, rack, alternator, brakes, and brake booster into the A31 (coincidentally also an RB20E auto model). So its mostly compatible. Suspension struts/coilovers are more compatible with the S13. Diff was the same as an R32... or maybe it was an S13... i'm not actually sure on that one, we used a mechanical 1.5 way in any case. A viscous LSD will only last you so long, but if its for regular street use and not track use, then it'll be fine.
A31 strutbraces can be bought out of thailand/malaysia pretty cheaply, they're decent quality too (or you can get em from australia, either way you'll get stung with shipping though). You can't fit R32 strutbraces onto an A31, because the R32 ones are 2 bolt and the A31's are 3 bolt. Your best bet would be an adjustable S13 brace (3 bolt), as the distance between the towers of the S13 and A31 are slightly different.