This is the catch. An RB26 has to be prepped considerable to run on a road course. water jacket mods, oil baffle mods, oil cooling ect ect. If these are not completed even a bone stock rb26 will die after a few all laps on a high speed course. the JGTC cars are kinda in the same boat as german touring cars. They a heavily modified compared to there stock counterparts.
As far as drag racing goes.... An aftermarket oil pump, cooler and water pump, head work, cams, big turbo (S) and good tuning can generate 700+ reliable RWHP and can be use as a daily driver. This is not myth. I have a close friend here in Japan and several acquaintances that are pushing that kinda power... running there car often and driving to work daily for over 3 years now.
RB26s are not good road course motors unless heavily modified but drag motors they are very well suited. Id take an rb over just about any other motor anytime. Now before I get pinged I did say almost any motor.