Id say T88-38gk for various reasons, cost, better compressor housing, we dynoed our drag GTR and made 907whp @ 2.5bar boost @ 6700rpm
Engine was HKS hideck with full tuned head.
Sounds like your engine is more than capable of producing the numbers.
Other than that I can offer you a Holset T95-R turho (Has) billet shot peened compressor wheel, 16cm housing so will spool very fast, it has inconel exhaust wheel. This will out spool T51-R + T88-GK due to the housing size, it will also make 900~1000hp depending on engine.
PM me if you want more information
how much price difference is there between the holset and the other two?