Assuming a stock tire, which was 27" in diameter for the TF trucks, in 4th gear (.71 overdrive) and a 3.36 rear gear, you should only be turning about 2073 rpm at 70 mph. With the 2.73, you only be turning 1681.
With my setup, I'm running a 3 speed w/B-W overdrive and 30" tires. Rear gear is stock 3.90. At 70 mph, I'm only turning 1850 rpm.
