Skim head , if warped or you want it to look clean! Slight increase in compression ratio. Thought the longer stroke affected bore ware more than bottom end. I rebuilt a 1500 engine and did 20k hard miles in it and it was still fine. Had skim on head and ported myself, ran on mobile 1 when it was 5w40 no problems till they changed it to 0w40 then the oil light would flicker at tick over . Changed to a 10w40 full synthetic. Payen gasket set, did not think they were expensive, never had a problem with them.