I have this same kit as well and love it. As noted this will only work with trucks that have a factory installed gooseneck/5th wheel prep package - often called “pucks.” They work really slick so if possible look for a truck that has this factory package. (As far as I know the puck system can’t be done aftermarket.)
Our old truck was pre-factory package so we went with a B&W turnoverball hitch that mommy_peanut mentioned. You just need to make sure to use it once in a while so that it doesn’t get stuck.
Turnoverball Gooseneck Hitch
If the GN has any sort of V to the front to it you should be fine with a 6’ bed.
Our truck has a bed camera that makes hooking up the GN super easy. The poor man’s version that I used with our old truck was to prop my phone or iPad on the back seat aimed at the bed in video mode.