well he does have the right idea. but smaller turbos dont flow like larger turbos. so you cant get too small of a turbo and expect it to keep up with the flow of such a large engine at higher RPM's with out it over spooling.
look at some turbomaps and flow charts. choose one that will create w/e PSI you want at w/e RPM yo uwant and then afterthat turbo timers and electronic boost controllers will take car of keeping your torque and boost curves as flat as possible up untill redline.
after talking another look at your dyno chart. you may look at 2 T3/T4 hybrids. look
here for a little tutorial on how to read compressor maps.
now assumeing 100% engine displacement efficency and 70% turbo efficency your engine will be using in excess of 60lbs/min of air if runing 10psi of boost. now yo usay you only want to run 7psi maxx. on an 8.7:1 with some ignition retardation you could easily run 10psi on pump gas, maybe even 15psi. and when you dont feel like buying premeiom you can buy plus and when you dont feel like buying plus buy regular and just turn your boost down... its as simple as a twist of a knob on manualy controlled boost controller or a push of a button on electronically controlled boost controller.
question that came to my mine... is this engine carburated? if so look for some fule injection heads or drop the turbo idea. tuning a carburated turbo engine is very hard and a pain in the ass. but it can be done. its just my reccomendation not to. you will see a torque cruve flatten out just by transfering to fule injection.
we need Saab in here. he is a turbo guru. or Hypsi87. if they dont find this thread soon try PMing one of them.