First, I search for "Pre Emissions" trucks. Most 2007 models back are pre emissions trucks. From the early 2000 models thru late in the decade, Cat engines dominated the SportChassis production. From around '04 on, MBZ started infiltrating that market. From all the research we have done, in that era, the MBZ was the clear choice. Regular reports of 500,000 miles to 1 million miles with nothing more than regular maintenance. Also, the MBZ engine's track record of fuel mileage seems to be better than Cat. While I am a fan of the 3126 series Cats, I am not a fan of the C7's.
What the folks at SC told me 2 weeks ago is Cummins power is back under the hood of the SC production. Early reports are good as to performance and fuel mileage. Caution: If you are considering an FL, the pre emmission trucks are sought after and bring premium dollars. Performance of the emissions trucks is less and fuel mileage is worse. That is why when you go shopping, you will see a glut of NEW SC's on the market in the years from '08 thru '10's.