to SIZE a turbo to a given engine....you need to figure the CFM requirement of "said engine".
Its Mathematical.
CID X RPM / 3456 = CFM
You need a turbo that will "spool" on "said" engine.
Its easy to OVER-SPIN, or UNDER-SPIN a turbocharger.....because turbochargers require airflow to rotate......and there are a MILLION + different sizes.
I have answered these questions over and over for people here....you dont want to take my advice....fair enough, good luck.
A GT45 will make 500-650 hp...fairly easy...but will run out of CFM around 650hp....and in turn overheat the charge air and detonation will soon follow.
650hp is NOTHING......it doesnt take 700cfm......and turbochargers are available from 150cfm to 1500 cfm....its all about the size of the compressor and turbine wheels'.
For your setup and goals....a GT45 chinese turbocharger is a good fit.
You can reach your goal on LESS than 14psi.