Here is the deal. 7050lb is a pretty good GVWR. EXCEPT for a King Ranch. All the stuff in the truck that make it a King Ranch also make it a heavy truck, and a heavy truck takes up a lot of that 7050. I believe you will be close if not over loaded. However since you are out of warranty anyway. Not a big deal. your truck won't implode if it is over GVWR a tad.
Not having a trany cooler, and towing in OD is what caused your trany problem. Other than that. IF you don't load 2000lb in to the TT (And I bet you won't) you should be OK. The 5.4 is a great towing engine. It will rev. But it would move the world, IF you just had a place to put it. I have been towing with my 5.4 for 10 years, up and down the mountains and I have yet to tax it, or even use all of the power it has to offer. I also have a 3.55