I have a 02 Chevy 2500hd with the 8.1 liter engine. I'm considering putting a 6in Fabtech suspension lift kit on it, probably going to fit between somewhere between 35" and 38" tires. The only think that's holding me is that I don't want to lose towing capacity. If i where to do this how much would it effect my ability to haul heavy loads? Also i have the Allison trany on it.