I had a 03 2500 Durmax with extended cab 2WD and now have a 06 2500 Duramax crew cab 4 WD. I took the Timbrens off the 03 and put them on the 06. The new truck tows our 33-5v Arctic Fox much better than the 03. It not power I am talking about but just the way the truck rides and handles with the fiver. I know the towing cap. of the newer truck is less than the old truck. The new truck is a LBZ. I have changed the tires on the new truck to 265 but have only towed the fiver to a rv dealer and back for service. I went about 90 miles round trip. I cannot tell any diffference in towing with the new tires but the ride is much better empty.:D

The increase in wheel base between your old extended cab and the new crew cab does amazing things for handling. I also think the 4wd is better balanced and handles better than the 2wd even in the same cab\bed configuration.