Turbo build: Need your advice

[cerial]

With your compression ratio you are going to only be boosting at higher rooms. You are going to be running premium and meth to keep things from pinning.
If you want to run pump gas you can lower your CR down to 8.5 or 9. But, you are going to be loosing low end torque. The turbo will need to produce more psi on a lower CR engine to make the same hp as the higher CR engine which needs less psi and less spool time.
It all comes down to proper tuning.
This all being said your talking like 600hp at the crank. That is going to take a bag of tricks to avoid running anything except premium. The amount of time not filling those cylinders with fuel when there is no need to do so will be a large factor in mileage.
I prefer to keep the engine simple and make power through gearing. For 10k you could install a 6 or 8 speed that would make more power at the wheels then a 700hp engine.
Once again it is all about tuning.
But, running 550ft/lbs With a 3.73 ratio yeilds around 2000 lbs at the wheels.
Running 450ft/lbs with a 4.56 ratio yeilds around the same 2000lbs. The difference between a 550lb and 450lb engine is massive reliabity wise.
Having a transmission that can lower the highway rpm to a ratio less then that of the t56 lets you have more rear gear. That all being said I did not even factor in the torque multiplied by the transmission or the reduction in lost rpm during shifts which leads to increased torque and increased acceleration.
All comes down to making it all work ttogether and what your goals are.