Our 99' 100 on 33 MTs and fully armored would cruise 80 for the most part. It got a solid 12mpg. It did a lot of down shifting but it was freaking plush on the highway and on the trail. I went back to a 1st gen Tacoma because they are cheap and light. LC is a heavy pig and those rear lower control arms love getting bent!
The tuned higher output 4.7 in a Sequoia at 80mph crossing Nevada and Utah would cruise at 80 but it wasn’t a leisurely cruise lol. The 4.7 in 100 got a lazy leisure tune it’s working hard to haul that brick at 80 lol. Yeah it does it but I would never call 3200-3500 down shifts to 4000rpm a easy cruise lol. The 05 Yukon I have run that same route towing a 25ft 8.5ft wide roof height 1800lb trailer at 75-80 was doing 3000rpm with down shifts to 3800 on hills lol. The LC or the higher output Sequoia would have been pegged flat out at 5600rpm trying to do the same haul.
My new 10spd 3.5 Expedition is a mellow sub 3000 rpm at 80 lol.
The lower speed stuff the LC is fine but its not even remotely as relaxed as the higher output Sequoias or the Tundras in those cases.