The "Long Block" which is the only 603 reman engine that you can buy from MB comes with block assembly, head, valve cover, oil pan. It does not come with injection pump ,thermostat, water pump or any other outside bolt on items you must use your old ones. The rebuilt has rods with a new design as well as a new designed head and from what I have heard its better and doesn't bend rods. It is guranteed for 4 yrs or 50 thousand miles which ever comes first. Do a search on 350 Motors and I'm sure you'll find more info.