Years ago the frame required the hitch to be 18″ to the top of the ball. In more modern times, different axles, frame changes, couplers and the 15″ wheels require a different hitch height.
We suggest a 19′ to 20″ hitch height to the top of the ball. We have seen some use 21″ for ball height and prefer it, though we suggest 19 to 20″.