Ok...so I've only every heard it referred to as a 'Pre-Alpha'. When I went to order the transom seal gasket, there are a lot of models apparently (MC-1, R, MR, Alpha 1, Alpha 1-GenII, etc).
Now...I know mine's not an Alpha. Mercruiser (according to the online exploded parts view at my local dealer) has done away with the gasket ring for my model and gone to a flat gasket that covers most of the outdrive.
On the one hand that's probably not all bad right, but that's assuming my 30 year old gimbal housing is still flat & level, etc.
I can't find anything really that identifies it besides the 898...is that really the entire power plant & drive model number? I mean, the outdrive even is stickered as an '898'.