I went to MT last summer from CT and back. First tow with truck ('99 CC SB 4WD) and Prowler 25'.
The early 6.8's were 2V the later ('03+?) we're 3V. The 3V had much more HP than the 2V. Mine has a 3 speed + OD auto and 4.30 gears. It also has a BANKS TransCommand Trans controller. No Tow/Haul in these older models. I was getting 6-9 in the city and hilly terrain, and 10-12 on the flats. Flat ran out of power on long/steep hills. Especially if I couldn't get a running start. If that happened, 45mph was all.......oh yeah, wide open throttle=no A/C. I am currently getting ready to put in an order for a new truck. It will be a diesel!
NOTE: the original owner had put a full banks big dog exhaust headers to tip, banks ram air filter and the Trans command. I'm sure all this helped and I didn't have to lay out the cash for it!
MikeH