gear change....possible gain?

You didn't say what your RPM is as you cross the line; from the MPH you posted, and working backwards, you're turning about 5550rpm. Am I close?

Using that calculated number for rpm, switching to 28 inch tall tire, and 4.10 gears I crunched the numbers and you slowed down to 113mph, not sure what the gear change would do to your 60ft; it may drop it and then that would drop you ET.

You stated that you already have 4.10 gears, put them into the car, if you don't like them, take them back out. It's only 34 nuts each way and bench pressing a center section under the car.

Good luck!