superk

My buddy has finally decided to do the single conversion. He is trying to climb back to my level even though it is such an overwhelming task For this I give him credit and now I have decided to help him out a little. He can pretty much choose any turbo size he wants since he has a link to get garret turbos at a very good deal. He wants something that is gonna make big power( comparable to a t78 or a bit bigger). What would be a good exhaust/compressor size? He is running a greddy front mount, greddy elbow, power fc, apexi gt exhaust, midpipe, unorthadox pully set. The motor is not built yet but will be getting done a little down the road. He has been looking at the hks exhaust manifold and a 50mm wastegate. Any help would be appreciated.
Thanks