It depends on the transmission. My 3ton '52 coe has a 5 speed with overdrive, two speed rear. I've had it up to a blistering 47mph. I don't have a tach, but I'd say that was about topped out. That was unloaded downhill and entirely fast enough, by the way. You may get a few more rpm from the small block but I'll bet that'll be in the ballpark.
