purchased a 2006 Silverado 2500 single cab with 63,000 miles for $8000. Going to be using this to spray out of. now i am looking for a 4 door 4x4 2500 or f250 to pull my 18 ft trailer with. Trailer is 7000lbs rated. Don't ever put more than 5000 on it though. Would you get gas or diesel? I'm leaning towards gas b/c less maintenance & cheaper gas. But will it struggle and gas mileage be horrible?