We used 550s at work in the oil and gas industry. They are pretty heavy trucks.
What year is it? Ford Diesel trucks are very expensive to maintain. Keep that in mind.
96 aero nose ford with a 460. The 460 is what I'm interested in because I absolutely despise diesels (no offense) but I have had great luck with 460s in my other trucks.
Probably less power than a diesel but I'm familiar with 460s