We have LT tires on our 07 and it does make a difference. Still, 7400 is more than I would tow with either of them.
Before the Expys I had four Econolines and yes they are towing monsters. The downside is they just are not all that comfortable and a 4x4 conversion is expensive. Even used they carry a hefty price tag.
I had a chance at a Excursion when I bought the 03 Expys. It too had P tires, a 5.4 engine and needed the rear end stiffened back up. The MPG was worse, it was less comfortable and wouldn't fit in the garage, so the added expense wasn't worth it. It may have had a better tongue rating but it would have been more of a dog in the mountains and as a daily driver, it would have sucked.
Expys are good trucks within their limitations but I wouldn't touch the trailer the OP is asking about.