Your 60' vary that much? You put down 420 to the wheels on spray?
If that's the case you're not leaving a ton on the table. I've a built 6.0 LQ4, with a healthy cam, 3.73s, bolt-ons, 3000 stall, and it put down 417 at the wheels on motor. Now my heads were portmatched with a dremel, but I consider them stock. Thats the way I was running it tonight, my spray isn't hooked up :ninja:.