My buddy Simon has a 911 about your body style with a turbo rotary in it. He bought some race tranny from Eddie Bello (Porsche drag racer) and its a pretty scary ride. He's got it on ET streets and as best as they can tell, puts down about 450hp at the tires backing in and out of the throttle to keep the car pointing in the same general direction.

Moral of the story, build the motor to the point of breaking the tranny