Rarity?

... It was a question based on trying to find proper MC for it at parts store. ...
You stirred up a lot, but to answer your question, the correct MC isn't related to the engine, only to whether you have front drums or disks, and power or manual brakes. Check rockauto for PN's. But, you can also change to a more modern aluminum MC by using a 2 to 4 adapter plate ($30 ebay, or buy w/ an MC for ~$100 from Dr Diff).

Welcome to the slant forum. Many people with strong opinions here, but also a lot of useful knowledge. Just use a coarse filter to ignore comments which might upset you.