Hi George
There is a huge amount of information on compatibility of parts and where to get your restoration done. Use the search.
MC21 cylinders won't fit an MC18.
There are a few companies in the UK that replate cylinders. I have used Aptec and others have used Langcourt. It's important to ensure there is no crack on the exhaust port. Otherwise it will fail.
GT Performance are a good place for crank rebuilds
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