The best I understand, McCulloch sold out to some company in Italy. Quite some time ago. There may have been other sales, because the last saw I worked on that said McCulloch on it had an MTD model number.
MTD wants to trade on the old brand names but the quality is just no longer there.
I don't think anybody has parts for the old 'genuine' MCCs, but if you can come up with a part number you may find one on Ebay or some place like that.