Too many variables mate...
I've seen 450hp from -7, 600hp from -5, not too sure about -10 (don't know anyone with this set-up)
Generally the -5 is a good 500rpm laggier then the -7... But since you have the 2.7 this will narrow it down..
Rb26 Turbo Upgrade, All Dyno Results - Skylines Australia
Have a read.. Worth it's weight (if any
) in Gold!
Good luck bud