I dont think it takes quite that much. I'm making 460whp out of my L28 without much done to the motor itself. completely stock head/cam/valvetrain, motor is bored .080" over with Ross forged pistons, stock 240z rods, stock crank, ARP hardware and a metal headgasket. Alot of the supporting hardware (fuel supply, exhaust,etc) is gonna cost $$ either way you go.
Since we're talking about actually driving our cars in this thread, I love that i can pick up and drive my Z anywhere and get 28mpg. I dont know many v8's that can boast both the 1/4mile times, hp numbers AND MPG numbers.
All out race car, the V8 is hard to beat. A car you actually take long trips on? Like I said I get 28mpg cruising and I run the car on pump gas and 25 pounds of boost every day.