[A/S] Hitch height help

["daydreamer36535" <3strong@xxxxxxxxxxx>]

 Hi,
I am getting my hitch hooked up and from my manual (1974 ambassador) 
I see it needs to be 191/2" to the top of the ball.
 
With the newer taller trucks, is this figure still good?
 
Is that in an unloaded or loaded truck?
 

I am trying not to take the whole rig to a welder, as the ball is not 
adjustable and needs to be lowered. Do you just put the hitch head in 
the receiver and measure?
 
Thanks for your time,
Joe