Did some more thinking about this...not sure what was going through my head earlier on the E30 flywheel bit, unless I was really thinking E36, which makes more sense/there are lots of E36 M50 products around.
No, it's a completely different trans -- Getrag 260 on the E30 versus a 220. The 220 was a weak replacement for the "adequate" 260. They have the same bellhousing bolt pattern. As far as bellhousing depth and the like -- I don't know the specifics, but the slave cylinders are different. So, you might have to replace the slave cylinder while in there. The other concern is whether the friction disk will fit on the input shaft, because the shafts are somewhat trans specific. So I'd be really surprised if an E30 flywheel could be made to work...
best, whit