Since you have the head off, you "might as well" send it to a good automotive machine shop and have them go over it. They'll clean it, tell you if it needs to be resurfaced (they may just want to take a skim cut anyway, which I think is fine if it hasn't been done before), they'll check the valves, guides, and springs; change the stem seals, etc. Shouldn't cost more than $300. Money better spent than screwing around with it yourself, imo.

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1987 W201 190D