[Fishin2dMax]

Welcome to the forum. Based on your information, you must be purchasing a single rear wheel 3500 HD. I have a 19, GMC 3500 HD SB single rear wheels with 6.5" bed and the good news I haven't needed a slider. One of the advantages of the new GM "standard bed" / Short bed truck is the bed is longer (6' 7") than previous years most and the mounting ball is 2" to rear of the rear axle. This extra 2" allows just enough extra room between cap of trailer and the cab of truck to negotiate tight turns without hitting the back of the truck cab. Of course, if not being careful, you could find yourself in a tight situation where there is significant elevation difference between truck and trailer and in tight turn that could hit the truck, but should that rare awkward situation ever occur, you'd just need to be careful when making the turn. With that truck, I really doubt you will need to use a slider hitch.