a cummins and a duramax. ive ruled out ford b/c of all of the poor reviews ive read. i dont know too much about diesels besides that ive just recently fell in love with them. i am looking at 04-06 models. i know both have their small problems but im looking for the best fit for me. i dont tow at all besides a flatbed trailer with brush sometimes. i am looking more at speed. from what ive heard the duramaxes are quicker. i plan on making upgrades starting with intake, exhaust, chip and tranny upgrades. thanks for any help.