Steve
The build date on my car is 01B (2nd week of January 67). The date code on my M/C is 341 which I think is December 7, 66. That would be reasonable for my car. I do not know if the MC is original but I suspect it is. I have receipts for the work done on my car by the previous owner dating back to 1975. I suppose the M/C could have been replaced prior to 1975 but that doesn't seem realistic since at most it would have been 8 years old and they rarely go bad.
Daral