the 07 6.0s are the best 6.0s out there.. i wouldnt have any reservations with it.. esp at 37k.. thats light mileage for a 07 in myopinion but alot of these trucks have low mileage.. as far as the 08.. i would stay far far away from the 6.4s they are HORRIBLE... the 07 would be your best bet.. but i wouldnt pay more than say 25-26 k for it.. i dont see 30k nowhere.. but if you get a 6.0l you will be just fine.. i drive one everyday for work and love it..