Heavy D , Used truck

Few things; I would ask why the head got replaced. If the engine over heated I would not buy it. ISX is a good engine and 425K is still young. How many hours though? The parts they have replaced are the main ones, so the engine should be good other than little things. The real concern is the condition of the after treatment stuff. This truck is at the age where the DOC is probably worn out and ready to be replaced. The DPF probably needs to be cleaned as well. If they have been serviced recently, or they can show it does a regen properly, then you should be ok. If they have nothing to prove the after treatment has been serviced then expect big bucks with that soon.