Gibson HR31 comes to mind
RB20DET-R, GTS-R turbo (im guessing hi-flowed), lumpy as f**k cams, ported head, cosworth pistons
460rwhp @ 8,000rpm on 1.7bar (24.6psi) of boost
But I guess with a factoruy backed budget anything is achievable
In the end I dont think anyone who aims for this amount of power is looking for a streetable RB20DET, although Im keeping mine registered to have some fun....
*here it comes...DAMN STREEEEEEEEEEEEEEET RACERS
EDIT: thanks legend 01
Im going to be running the same turbo and exhaust manifold, a Jun intake plenum, 040 pump, 550 jectors, remapped ecu, and maybe cam gears, should get 260rwkw on 18-20psi with some luck
-Jez