You need the manual flywheel, the auto has a pressure plate and won't work unless you get a 10k RPM clutch setup.
The driveshaft is iffy. On my ZXT I used an NA 5 speed and had to have a custom driveshaft made (NA trans output shaft to ZX Turbo diff) or you can swap the pinion flange on the differential. Not many people mention this so I guess it's all the luck of the draw.
300zx input shaft and bellhousing is different according to what I've read online, but I've never tried it. Any L series transmission from 70-83 bolts up. For the KA tranny, you need an L series bellhousing and you have to get it machined to accept certain parts (I think some bearings and shafts). The write up is on here, as well as a few people that offer that service.
I've got an extra 4 speed, and I might have a 5 speed soon but the 2nd gear synchros are going out.
Mario