My '51 1-tonner had 5.14 gears and would have been flat out at 50 mph. 35 - 40 was comfortable. I've changed up to 4.10 and now 50 is practical all day long. I'd say, jbc, that 40 - 45 is okay for yours.

1951 3800

Be the change you want to see.
-hotshoe