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I would be tempted to sort the valve seats and dress the damage carefully with a dremel. I don't think it will make a jot of difference, you wont be racing it no doubt. Others may think different but it is your money.
That one above looks definitely as if the cylinder has ingested something, there's a huge difference between that one and the original subject. Also more pronounced damage up in the centre where something has rattled around.They are quite a radical spec when you look at the numbers they run. About 110bhp per liter capacity, that's a lot for a two valve engine even today. That 285 cam would also be quite hefty in a car engine with just marginal tickover stability, reasonable torque spread plus higher rpm flow. Usually known as a rally / mild race grind.I'd guess from the rpm range, compression ratio, cam timing etc you've got to be fairly diligent in setting up these twins to really get them running spot on. My perception in reading other info about them is that cam problems seem to crop up a fair amount, what would others see?