[Luckystrike]

I was wondering, What was it that you did not like about your 5.9 Cummins diesel? until you mentioned that you were only getting 10 m.p.g. There has to be something drasticly wrong. My 5.9 Cummins averages 24 m.p.g. and i've driven it for 13 years and 312K miles with the only repairs being a water pump and a starter.
You should be getting at least 20+ m.p.g.
In my opinion, concerning diesel trucks, there's no better combination of performance, reliability, and economy out there than the 5.9 Cummins. If I were you, I would find out whats wrong with the Cummins, get it fixed, and keep it.