127 mph @ 3700 lbs puts you right around 600 hp which is what I'd expect from those parts.

If you have good headers and a good oiling system then an upgrade to a solid roller will pick up some power. Fully porting the intake will pick up power too but it is expensive. I used a fully ported M1 4500 on my pump gas 470 and we made over 700 hp but it was a very expensive intake. Probably cost $2000 to duplicate it these days since it was cut open and then welded back together. There are more choices for an RB intake. Maybe the std port version of the Super Victor for example. Sticking with the 4150 carb will cost you some power. Are you willing to put a scoop on the car? Do you have fresh air to the carb?

The cam I used was a custom 264/268 that Dwayne had ground. That same cam should work for you or he might have something that would work even better. You will probably need a looser converter to keep the engine in the power band all the way down the track. Something in the low 6000 range for the shift fall back should work but you would need to spend some time with a converter rep.

I think the 4.30 gear would work since the engine should make peak power right around 7000 rpm. The converter will probably slip around 10% so driveshaft speed is 6300 which works out to roughly 130 mph.