You can use some tools found in the Tech Tips. Using a Ratio Calculator

With the info you provided, 6000 RPM, 3.23 rear end and SM420 and 28" tires you were going 154 mph.

I hope your brakes are good!

SWEET
Sergeant At Arms: Old Dominion Stovebolt Society
BUNS?!?!?!Where we're going, we don't need no buns.....
1950 GMC 450
1951 Chevy 1/2-Ton
The GreenMachine
In the Stovebolt Gallery