It's not essential, the gaskets can usually be used a couple of times but does depend on the state their in. As they are copper, if you can get them out in one piece, you could theoretically anneal them (make them soft again). However, it's probably worth putting new ones in because the last thing you want to have to do is go through the hassle of removing the headers for a second time because they start ticking due to a leak at the ports.

They're about a fiver each from a dealer. I don't think you'll easily find them anywhere else?

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