Well as it turns out the dealer was full of @##$ on the trailer weight,the gvwr is 8000. I had the trailer loaded to 7800lbs and the 6.0L gas engine imo sucks pulling that kind of weight.
If you like going 40mph up a grade with the engine screaming the entire time, thats fine but not for me.I think it's like driving a 16d framing nail with a tack hammer. The tack hammer will eventually beat that 16d in but it's just not the right tool for the job.
I traded in that gas motor for a 2004 LLY Duramax and the difference is astonishing. The diesel tugs that 7800lbs up grades at 65mph without breaking a sweat. Another big + is MPG that 6.0L with 4.10 gears thought gas was free,10-12mpg empty at 75 , 5-7mpg pulling the bigger trailer at about 55 average. The diesel got 17.7empty at 75mph and 11mpg tugging the trailer at 65mph.
So there you have it,having tried pulling a 7800lb trailer with a 6.0L gas engine I would NEVER EVER recommend it to someone else. But if you are a person that likes crawling up a hill with your foot mashed on the floor and your truck screaming then use the 6.0L gas engine.