buying used 5th wheel

If you load the trailer to near capacity lets say 12k and using twenty percent so tongue weight which is considered about average you have 2400 lbs plus anything you put in the bed. That is close if not over on that truck but it will likely handle it. I would look for a little lighter trailer or a bigger truck. As for the slider hitch you may want to look at a revolution pin box.that way you can use a standard hitch and because you are used to pulling a trailer instead of a fifth wheel it make may be more to your liking as it will track and act more like a trailer as the pivot point is move d back to give more clearance. JMO