The only reason the OEM lists as a Class 2 is the factory tow rating of 3500#. They can’t sell you a hitch rated over the factory specs or they are implying you can tow more. If you look at the OEM hitch itself it’s easily a Class3. Replacing it is a waste of money.
No wiring harness?? Installed the Ford OEM one this week and it was literally 4 bolts. What takes all the time is the wiring. Plan half a day for that.