If you are staying naturally aspirated, you only have so much torque to work with. Outside of increasing displacement or a significant bump in compression ratio, you have to use RPM to make more power. The upper torque limit on a 11.0:1 CR mill that I have seen is about 340ft-lbs rwtq (at roughly 4700 RPM). If you managed to make that torque at 6500RPM, which I haven't even heard of, you are only looking at 420 to the wheels.
6500 is just a tune away on a stock rotating assembly. Most quality built shortblocks can easily handle 7000-7500 RPM . A decent set of springs is all you need to fortify your valvetrain to handle more RPM.
Believe it or not, the Trick Flow heads can easily flow enough air to support 8500 RPM on just 4.6 liters (but don't try it without the rest of your setup being able to support that as well). With the right setup, you truly are only limited by your RPM. You will need a full exhaust, a proper cam selection, and an optimized intake setup to feed either TF or ported 2V heads. That includes the TF intake with its very generous 9 liter plenum volume. It will work well to at least 7500 RPM. Beyond that you are looking at a custom sheet metal intake.
It may not be the best combination down low in the RPM range, but as far as peak power and power under the curve is concerned NA, you would have to spool a 4V very high to make more power than a fully built TF 2V setup, and it would need a good bit of work as well just to keep up, let alone exceed the TF setup.