Then take a 2.8 18v and put there forged pistons with a target CR 8:0. With a proper mapping you'll get your 270hp at 0.6-7 bars of boost (stock it's 250hp at 0.8 bar CR 7.3:1) you'll have a very drivable car with a good torque control, and you'll reach 370hp with 3200gt turbos. These turbos make 380hp on the 3.2 v8. However going to 8000 rpm would be totally useless, the head flow capacity would be exceeded way before, probably at 5000. You might succeed to improve the heads VE but to do what, if you already had the power you wanted ?
I'm surprised you are only talking about the power, while the time is won with the torque. Power is just for max speed. If you just want 370hp at 8000 (and not a drivable, broad band torquey engine) then it requires 330nm, using a 2.8 displacement v6 turbo engine becomes overkill. A good 2.0 4 cyl turbo engine would do the job. Or you may want to run a low boost level, but then biturbo heads don't flow well enough, including the 24v. An engine is a machine, a machine has physical constraints and reasons.
I'm surprised you are only talking about the power, while the time is won with the torque. Power is just for max speed. If you just want 370hp at 8000 (and not a drivable, broad band torquey engine) then it requires 330nm, using a 2.8 displacement v6 turbo engine becomes overkill. A good 2.0 4 cyl turbo engine would do the job. Or you may want to run a low boost level, but then biturbo heads don't flow well enough, including the 24v. An engine is a machine, a machine has physical constraints and reasons.