If it is the short box CC version, GM says to not do 5th wheel or gooseneck. Either way, I wouldn't do it with a 5.3L and 3.08 diff ratio. Are you sure the 12,200 GVWR you mention is not GCWR? Big difference. Once you factor out the weight of the pickup, all of everything you have on board, full tank, etc... there really isn't all that much left for what you can pull. At least not much when it comes to doing what most folks do with a 5th wheel or gooseneck.

Reason I question the GVWR you mention of 12,200, and payload of 2007 lb, that would mean the pickup itself would weigh in, all by itself, at over 10,000 lb, which we know is ridiculous for a 1500. So the 12,200 has to be Gross Combination Weight Rating (GCWR). My 2015 2500HD LT Z71 with snow plow prep comes in at around 7300 lb with full tank and the wife and I on board with about 200 lb of tool box in the back. Take the weight of the 1500, add in that 2007 lb on board, and you are not going to have half of that 12,200 lb available for trailer!

 

I have had many chevy trucks and towed travel trailers with all of them. I always pushed the weight beyond the ratings but would never pull a fifth wheeler with a half ton. (unless it was a baby one) Bumper pull trailers will work great on a half ton if you get the proper weight distributing hitch and also set it up properly. I actually towed a 34' bumper pull that weighed in about 8000#'s with my half ton but I was probably over my axle weight. (it was a 2007, some of the newer trucks have a bit higher ratings) It pulled great but I did change the ring and pinion to 4.11's. I finally broke down and bought a 2500HD 4x4 and now they feel like they are one unit....and don't forget the trailer brakes....

You can change the gearing for about 1000. but you do have to have the ECM calibrated afterwards. Good time to have the AFM turned off if your truck has it.

 

Depends on what you have....mine is a 39' Montana with a dry weight of 13,000 lbs. I use my 2014HD3500 GMC Diesel 4X4 to pull it. Can't even tell it's back there. I also have a 1990 GMC 1500 (350 gas) that I would hesitate pulling much. Pulled a utility trailer from Alaska to California and the tranny went out a few months after I got here. Gears were standard for a 4X4.