Not good advice to buy a diesel truck to save money. A diesel pickup costs more to buy, more to maintain, and a great deal more to repair.
A 2500/3500 class truck is heavy duty with emphasis on heavy. The more weight that you move down the road the more fuel that will be burned.
With trucks going from a 3.42 to a 3.73 set of gears will increase your truck's towing capacity by 25%. You get a 25% increase going from 3.73 to 4.10 gears. Or going from a 3.42 to a 4.10 will give you more than a 50% gain in towing capacity. Check with your VIN what gears are on your truck. A $400-$800 gear swap would be a better move.
I have a diesel 2500 truck and it is great for hauling and towing but it is not something I would want as my daily driver vehicle. Even with IFS it still rides like a "truck".