I'm planning on putting a 3.07 '68 truck rearend in my 261 powered truck. I calculated out the gears, and the first three gears (with a 3.07) of the 4 speed Saginaw 3- groove I'm planning on putting in matches the 3 upper gears of an SM420/4.11 almost exactly when plotted on the same graph. So I'm getting an extra gear. It should give me about 2600 rpm at 65mph with my current tires. I'm upgrading the brakes, though.
