2020 GMC 2500 and Pullrite Superglide hitch for puck mount

I think you will find that your bed is longer plus GM placed their pucks so that the hitch point is 2-3" behind the axle centerline. I doubt that many will use an auto slider for that truck. You may want to measure from the gooseneck ball to your cab and see if you are going to have clearance issues. I have a friend who set up a B&W companion on his 2020 and the trailer's kingpin was positioned right over the gooseneck socket. He has had no issues not using a sliding hitch.