1shot,
You should be able to easily do 60 plus mph in your truck if the engine is in good shape.
I've spent time behind the wheel of a '56 and a '59 half ton truck, both with 235 and 3.90 rear gears and could cruise pretty comfortably at about 60-63 mph. It is not quiet though...some guys don't like to wind 'em that high.
