I usually take 5th in my Mustang at around 120

5th gear is too tall though, really drops you out of the powerband and it takes a bit of effort to get it to the governor (135, damned thing). It's got an insane powerband compared to a european or japanese car but at that speed a 2 ton car geared for highway cruising needs more beans than it's got. 6 speed and a built up engine will come when I get the $$$$.