ok ignore the modded T4 for a minute (and mike, just for the modded bit mike!), basically we all know a T4 will work for 500 and so will the GT30, so at the end of the day it comes down to whoever and however the person chooses to build the engine and how well it is speced and put together. old technology or new they both work for the the big 500
choosing either way they will have a quck car if done right!