You need to be specific to whoever builds it. If R200 diff, rear u-joint is limited to 1310 joint due to available flanges, although you can go to 1350 at tranny end. The basic slip yoke that JCI uses in the base model is cast and is pretty weak. John farms the driveshaft out to his local driveshaft shop. I would get at least a forged slip yoke if not a billet one. If you have a 240z, get a 3" tube. If 280z get a 3.5" tube (smaller tunnel in 240z). Aluminum is sexier but supposedly less strong inch to inch. And go ahead and make a safety loop. That's all I have learned (mostly the hard way). No matter who makes it talk to him first.