Brand new to the forum and about to be new 5er. Already learning a few things from reading posts and the one about actual GVWR, etc has me wondering. Will need to move up from our current 1/2 ton. ...
You will have 254lbs left for passengers and gear in the truck. That's cutting it pretty tight.
As for factory installed hitch vs. after market, go factory installed. I know in lighter vehicles, the manufacturer will limit tow capacity on vehicles with after market hitches because the chassis isn't beefed up to support the hitch. If you get it factory installed, then you know the chassis is built to support that hitch and what it's rated to handle.