I have a 85 C30 dually 2wd with a 6.5 turbo diesel. Thinking about swapping to a 12 valve for more power and torque for hauling my farm tractors around. I will tow loads upto 20k trailer weight. I hauled 6000lb last year and it did it fine but wouldn't try anything over 10,000lb. Truck has 54k original miles and is in amazing shape. Thinking about using the dodge nv4500 2wd so i don't have to use adapters. Truck currently has a SM465 granny 3 speed so I would gain overdrive too. I'm building my 83 idi up for towing but would be nice to have more. The c30 would have way more potential of a truck with more power. I love the 6.5 its bad ass but takes allot of the duallys towing capabilities.