I'm guessing GMC Denali.

If so the stem has a large clamp diameter but I've yet to determine if it's 31.8mm. If it is then you can get a bar of the same diameter and some brake levers (make sure you get levers that can be set up for cantilevers, as V-brake levers won't work as well with the Denali's calipers).

You can use the shifters from the Denali and you'll still have all 7 gears unless you're thinking of moving wheels over from your MTB, but that would really start to complicate things.