Generally speaking, I would prefer a gas engine over a diesel most of the time, just based on the high expense of fixing them and Ford’s history of poor diesel designs.
On the other hand, I would hesitate to be the first kid on the block to own a brand new engine design. Who knows if Ford is going to get the design right or if it is going to have problems? The days when you could assume that a new engine from a big manufacturer was going to be done right are over.
I have a Ford F250 with a 6.2 gas and I love it. I’m definitely not a Ford hater. But in your shoes, I might also look at the Ram equivalent (5500?). Spend some time on a Ram forum and ask questions there about the reliability and quality.
Offhand, I don’t know if GM offers a 550 equivalent or not, but if they do, I’d be checking on that also.
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I don't like to make plans. They cause the word "PREMEDITATED" to get used in court!
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My Body is a Temple! Ancient, Crumbling, Probably Cursed . . .