The lazy response on the larger carbs may have been due to the Torker intake.Maybe not

509 cams like compression and it should run well you will just have to be careful not to get into detonation in the upper rpms once you build some cylinder pressure.I bet it would like more initial advance.

I would thin an RPM intake or street dominator intake would be a better choice and would run at least a 750cfm carb if it were mine.

If you could sell your heads and get the 440 source heads you would be great on compression and likely run faster.