I am making some changes to my 68 which require a THM400 Driven gear change. When I got the car it was running the standard 14x6 wheel with 2.56 gears. I put on some 15x7s, and will shortly upgrade the rear gears. Need some help in determining the new Driven Gear to use.

Using my trusty Ames Performance catalog they give the following formula:
Number of Drive Teeth x Axle Ratio x Tire Revolutions per Mile all divided by 1001 to get the Number of Speedometer Driven Teeth.

My new Axle Ration is 3.08 (found NOS set via Smoke Signals)
My Tire Revolutions per Mile is 842
How do I determine my Number of Drive Teeth?

BTW - Engine and tranny are still in the car.