How about an old Muncie 4-speed?

I have one in my 65 C10.

Running 33" dia. rear tires the engine turns 2200 rpm's at 55 mph, 2500 rpm's at 65 mph.

The old Muncies were built for V-8 power, while the S-10 5 speeds were not.

Something to consider....

In the Stovebolt Gallery ~~ "The Orange Crate" 1965 C10 SWB Step Side Build Thread

Inspired to be different. Different in a way of my own, not in a way that others strive.