Mine got a ratio change, too, to 4.10. I don't know what rpm it turns yet at highway speeds, but I do know that 60 mph is now easy, where she was screaming before at 50 mph; so much that I'd never take it up that fast without a good load aboard. I've also gone to a 1981 250 c.i. inline engine recently, and what I have now is a truck that will easily keep up a highway speed, and is relatively smooth and quiet with 235/85R16 tires, and OEM brakes - which are adequate even when fully loaded.
Eventually, I might add the Gear Vendors overdrive unit to the SM420 transmission to bring the engine's speed down further on the highway, as I intend to drive the heck out of this thingy for several decades, yet, until I get too old.
