a-body headers

I have never had a leak although I customarily double gaskets. As far as the rubbing problem,...Instead of using the ball peen, take a short section of heavy guage steel pipe (like black pipe), lay down a rag or something similar and then give it a wack with a heavy hammer. This way you get a uniform indentation. I use a thin peice of rubber to lay down to avoid the pipe from moving when you whack it. It looks good too, almost as if they came that way. Its important to use a heavy hammer. Using the pipe also allows you to direct the angle of the crease that you may need.