Headman headers flanges

I have a buddy who has some Heddman headers he said I could have as mine are pooched. But he says that they will leak because of the small flanges, they are only 3/16 thick. Has anyone used these, or do all headmans use the thin flanges?
He is a mechanic and swears they will leak unless the really really good gaskets are used...advice!!!!!!
AL