Your trailer's hitch height is 17 3/4", according to the specs in the owner's manual.
The top of ball height, as a rule of thumb, should be ~1 higher, so ~18 3/4". But that can vary with tow vehicles suspension, (softer=higher stiff=lower).
add edit: if you changed the trailer tires to a different size, then you should add half the difference of the diameter of the old and new tires to the ball height. It's probably not enough difference to worry about.
2014 Silverado 1500 5.3L maximum trailering package (yes, I'm towing the 34')