Cummins c-13

When he said cali I ran out of options..

 

Ahhh-ha. Missed that little detail.

 

I would not touch the cummins with a 10 ft pole. The 07 with the 60 series will do the job no problem, make sure it's checked out properly. Dyno test, blow by test, oil sample by a real lab, and a full check by a good mechanic, tho this option would leave you out of California.
If you want new don't be afraid of a 13 lt engine, especially the Volvo and I shift. I hauled tri axels out of the maritimes with 65k in the box with mine, no sweat, and got great fuel mileage.
DON'T touch a cat with dual turbos, and dont touch a. At after 2007 for sure,, also, cat and paccar (Peterbilt and kenworth) are real proud of their parts and charge you they the nose for it. Even more than Volvo. Ill never own another.
Cheapest truck to maintain is still a freightshaker. DON'T buy a cascadia before 2012. I did, almost bankrupt me.
DO YOUR HOMEWORK BEFORE BUYING!!!!

 

Equipment Resource Group in Ayr has a KW T660 that averages over 9mpg for sale. Really nice looking and well spec'd truck.

 

358 rears with the DD13 is a little low, especially for mountains if your heavy. Also check the from axel, 12000lb is low and means you will have the 5th wheel far back to keep the axel under 12k, huge gap between tractor and trailer is a mpg killer. Set back front axel and short wheelbase need 13200lbs. I would not touch it with that axel.