To me I’m thinking the back cap of the upper housing suggests this drive is something different than any of the alpha type models plus the size of the overall housing and mounting surface area to name a few.
It could be more of an TR, TRS, MerCruiser II-TR 1973-1976 or any one of the numbered drives including SSM, etc..
I believe we’ll need much more information regarding the overall boat, engine / transmission if ones there? Year of boat, more photos of the engine compartment…
If possible, carefully clean up the lower left side of the sticker just below the 330 number to see if you can fully read the stern drive serial numbers more clearly/accurately… you can see the gear ratio on the right is 1:50…,
A little over half way down of the following link is a list of drive possibilities that it could fall into..
Lookup MerCruiser engine & stern drive by engine model and buy discount parts and accessories from our large online inventory.
www.marineengine.com
Post as much info about the boat as possible as this one could be a bit more challenging to pinpoint in my opinion.
Hard to tell but the top Transom serial number looks sort of something like
13579170
