Andy I think as far as gearing is concerned you might pick up a couple of hundredths if you went lower, if that. I believe you might pick up more with some chassis tuning. I did some tweaking in my drag program and it didn't really pick up much with a gearing change.
We have a 66 nova @2700 pounds, SBC that made 702hp at 7200 at the flywheel. This car typically runs 6.teens to 6.0s at around 112-114mph, 1.27-29 60' times. This is leaving at 3500 off of the tranny break, 5500 chance converter, 4.88 gears, 14x32 tire.
Looks to me you might be leaving some on the table early in the run. Just my .02 cents for what it is worth.
Curtis