had 15 2500hds in fleet I was manager for . All ran at least 9200# with utility beds and rail gear all the time with 19.5X245 tires all were automatics with 4:10 rearends been using this setup for over 20 years using 5.7 liters until the 6 liters came out. the 5.7s were good but the 6 liters seem bulletproof usually ran them to 250,000 miles only had one not make it (driver neglect) usually made that mileage in 6-7 years tried to order new at end of lease (6 yrs) and 250,000 miles drivers were on call 24/7 in all types of weather, and being idled from start to finish of call. Had very few tows. Transmissions usually lasted 175,000miles fuel pumps 100 to 120 thousand.