the 33/34 GT-R transfer case clutchpacks run some amount of preload (which is part of the reason why 33s and 34s oversteer less than 32s, as well as having ATTESA that updates more often), and which is why you usually have to disconnect the front drive-shaft to run 'em on a chassis dyno. But lots of drag 33s and 4s in Japan seem to have RWD switches, so it must be possible to modify the system, maybe just not cheaply.