I was looking at a 1982 30' Newport which I really liked however it had these valves. There's 5 I think. The owner said they've been working well for the past 40 yrs and he didn't seem concerned. I was concerned. And how about the corrosion? What could be doing that? It's either the intake or output for the head. Any ideas? Should I make an offer? What would be the ballpark for replacing with Marelon or bronze?