I'm confused now because from looking at the parts manual, the damaged head seems to be from a different model (looks like MC18) - there's something fishy going on here so not even sure yet how much of the bike is original. Could be up sh*t creek because who makes cylinder heads (let alone cylinders) for an 18 yr old bike? Unless I start to get really creative...kiwi ingenuity can only go so far 
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'87 MC16