I don't actually have a 6.5 in mine but my owners manual lists the tow capacity for diesel powered Silverado 2500s at 10,500lbs with either a 3.42 or a 4.10 gear. There is also a belt routing diagram under the hood for a 6.5 as well but my service manual doesn't list any engines other than the 5.3s and 6.0s for the 3/4 tons in those two years. I'm having a tough time finding any information so if anybody has got any ideas I'd be interested in hearing them. I figure they must exist somewhere or else they wouldn't have put the information in the owners manual. I'm thinking maybe some were installed in fleet vehicles but I can't find any information to back that up either.