I have a cousin who did brought R34 GT-T. He said the most he can churned from the engine is just 300hp, that's 20hp from the original. Also need to change oil frequently if always full throttle, which means the oil easily become so thin like water after excessive drive. He said the engine block of RB25 is so thin not like RB26, which not much engine bore can be done to up the engine displacement.

So my advice if you just wanna use standard engine without modding it just go for GT-T...if not get GT-R so you have lot's of options to increase the power..

R34 is too bulky for drifting, better go for S15..