But you have (except trans cooler) better gearing than a 10 year old half ton with 4.10 axle rated for 8k+ pounds. The difference in tow rating between 3.08 and 3.42 is less than 500 pounds. The HD towing group with trans cooler takes the 3.42 from 5500 pounds to 8000 just by having the trans cooler.
Be careful about adding a lot of weight to the rear of the RV. Frames are not usually designed to handle 500 pounds off the rear. And it can really upset the tongue weight percentage and handling.
Thank u I didn't know putting stuff on the bumper is not a good idea. I see people do it all the time. I don't begin to understand all the gearing "stuff" you guys are talking about. People like me expect the stated tow capacity to be the true capacity - not based on all these factors you have to figure out.