I currently have a 1990 extended cab K2500 that handles all my hauling and towing needs. But I also have a wife and 3 kids that I take with me while hauling stuff on 2+ hour trips. My neighbor has a 90's C3500 crew cab sitting in a field with no motor or transmission. I am considering picking it up for cheap and dropping in a new engine/tranny and using it to pull my equipment trailer (12000 lbs) and still have a family plus load hauler for longer trips.
My question is regarding the engine and transmission setup that will give me the best fuel mileage and be reliable. I know that some Dodges with the 5.9 12v Cummins and NV 4500 have been getting better than 20 mpg highway so that is what I am shooting for. But I think that the straight 5.9 swap would end up costing more than the truck is worth, unless I find a steal on a wreck. I am wondering if the 4BT Cummins would be a better option and if it could get the same fuel mileage. I am not locked in on diesel though as I know maintenance cost on diesel is higher.
I know that the 350/turbo 400 combo in my K2500 doesn't come close to getting the 20mpg I would like to see. I also know that the 4.3 v6 only gets 20mpg in a S-10 so I doubt it can pull the Crew Cab dually with much fuel mileage. I know that both LT1 and LS1 can get over 20 mpg in a Camaro but I don't think they would do it in a truck that weighs twice as much. I am not locked in to Chevy engines especially if there is something that will achieve my goals.
Am I insane to think I can get 20mpg empty out of a Crew Cab Dually? Does anyone have one that does? 20 is just a nice round number, so if it can only get 18-19 that is fine, I just want to get some brainstorming before I spend money, or dust off the engine hoist.
