I drag a 6x10 enclosed trailer down I95 all the time. It's no cummins but the 4.7 does a pretty decent job for me. It will pull at 80mph but it much prefers 70, especially when the air temp gets above 88F.
Shortly after buying the trailer I did have to rebuild my transmission (248K miles on the orig) and it showed heat on the clutch discs. I upgraded the torque converter to one with carbon fiber discs and braised fins that is built to take a bit more load than stock. I'm sure driving at 70mph could have extended the logevity but I can't stand all the dirty looks I get.