Is there any clues that will give you any idea if the head gasket has been replaced? I bought my truck a couple of months ago ( 98 5 speed,3500,2 wd,dually)there was an exaughst manifold bolt missing. I bought a new one from cummings and had a hard time getting it in because the gasket was bloking the hole some. After taking a small knife to it I was able to get the new bolt in . the truck has 200k on it ,Im just hopeing the head gasket has already been replaced. What can you look for ? thanks Otis