Re: stern drive?
You can't look up old drives by serial number alone. Had you posted what your engine year, and type was, then it would have been a lot easier to answer your question.
If this is the boat you have in your profile, 74 cavarelle beracuda IV,81 Arrowglass, i/o Merc 250cid 165hp, then yes you have a MC-1 drive, and it should be a 1.65 ratio.
After all that, what is it you are looking for or trying to fix?
PS: No such thing as a "Pre Alpha" that's after market speak for "Not sure what you call it"