Right place (I hope)
 

I have a 2005 GC (5.7 litter engine) and planning on a trip. I kind of scare of going I77 to 81. If I wasn't towing my wife's car on a tow dolly I wouldn't even be here. U-Haul says "Okay", but I guess they haven't driven this route. Would this be okay or should I find another way around the mountains?

If you go slow like 35 to 45 and not use over drive it should be fine just slow and use more gas.

i don't know that highway you're talking about, but here's my thoughts.

you've got plenty of power to pull that uphill. i'm sure it's the braking downhill you're worried about.
i would just take it easy and maybe even shift into 2 while descending anything steep. don't ride the brakes for long or you risk the case of overheating your brake fluid, and reducing your brake pressure. you can totally loose all brake pressure if it gets too hot.

not to scare you, but just take it easy if you can't go around.