Actually, the 4.6 needs MORE cubes than the LS1 to make power.
The 5.7 makes 61HP per cube in my car and the 4.6 makes 57HP per cube on the 260 rated engine. So the 5.7 has an additional 80HP in a lighter, stronger motor.
Add in the weight difference from a mustang to a vette and you actually DO need a blower to keep up. Even then I have pulled stock pullied mustangs before, so you actually may need MORE than a blower in some cases.
:number1