Cummins is by far the best out there as far as being reliable and yet still holds up with the competition it being a l6 and everything else a v8. There are a few duramaxes out there that have 6 speed manuals. I looked at one before I bought my truck and it was ok it was slightly on the beat side tho. Either route you go you will be happy with a diesel. I myself also came from a ole 318 dakota and the power is addicting so it the turbo whistle