Het Ryan,
That's a tough one cause there are other considerations. head gasket thickness? Are the heads milled at all?
valve sizes? If everything is stock, a guess would be in the .515 to .520. However the engine may not need that kind of lift, or it may need more depending on the use and other components. What duration and overlap are you contemplating with that lift? The cam, manifold, carbs, and exhaust, should all be picked to work together. Just making the valves open as far as they can is not a recipe for more power.
A call to one of the cam manufacturers could help you alot. I found them to be very helpful, and have axcess to way more info than I could ever catalogue.
Good Luck