The R200 doesn't have the strongest spider gears in the world. Spinning one wheel then hitting a high-traction surface can explode them. I popped one goofing around with a 220 hp 240Z. I've replaced a couple in customer Z32's. When everything is hooked up and going in a straight line, the NA diff is plenty strong. Output shafts are the weakest link. You won't kill one with 400hp if you aren't abusing it.