With -1 heads and a solid roller cam you might still be making power at 7000 rpm. Usually the power is dropping by 7000 rpm with those heads and 500 cubes but it all depends on compression, cam, intake and headers. If you have a good intake (ported by someone who knows what they are doing) the power will carry a little further. Most Mopar guys run cast intakes right out of the box which kills off some of the top end power. You'll have to drive the car for awhile to see if those 4.30 gears are what you want. From what I've seen, the 4.10 gears tend to work pretty good with a 500 inch engine but it depends on where the power curve ends up.