I know what it is and the difference between it and a 5th wheel hitch.

I am pretty sure I know the answer but have never verified.

I am guessing a GN hitch can only be used on a ball that is mounted in the bed. Cannot use a class 3 system mounted at the rear of a PU like a bumper pull type trailer. Correct?

The Goose neck puts the tongue weight of the trailer directly over the axle. If mounted to the rear hitch you will not be able to carry as much load.

quote:

I am guessing a GN hitch can only be used on a ball that is mounted in the bed. Cannot use a class 3 system mounted at the rear of a PU like a bumper pull type trailer. Correct?

Correct.

Affirmative