There is a lot of math involved to determine the exact
changes to moving weight bias rearward but obviously more is better, at least to a point. I doubt you will be able to go too far, though, w/o doing a lot of major reworking to the car.
If this is a drag car, it's interesting to know that raising the center of gravity helps traction by increasing weight transfer to the rear. That's why many early drag cars had a nose up stance and why the altereds had their engines mounted so high. Nowadays, good tires and suspensions (and rules) keep this to a minimum. Whether this is something you could use, depends.
FWIW, in '68 we had a '65 C10 pick up w/a 389 Pontiac mounted 18" rearward. It was the first vehicle (besides our wrecker
) that I drove that could pull the front wheels on takeoff. It had other modifications, but the engine moved rearward was the main thing responsible for the added traction.