Not anyone's first choice...but I have had twin SBC with alphas for last 25yrs..last 15 yrs mid 400hp (ZZ430 like components)...blown both upper gear cases once and some routine issues- other than that reliable. :)
Had to have the boat so a bit of a compromise-

Is it possible to change the thread title?
I found out it's a PRE-Alpha drive. It has the fins on the top sides and the lifting hook on the top plate.

It seems to be shifting fine off the boat. The boat side shifting works like it should.
I split the drive and replaced the impeller and pump housing, put it back together but now when I pressure test it the air comes out through the water transfer port on the upper. It doesn't hold any pressure at all. It's still off the boat hanging in the garage. I matched up the new gaskets to the old ones, put a big o-ring on the lower pump housing, and the big rubber wiper on the drive shaft above the pump.
Obviously I missed something or something else is wrong.
Any ideas?

As far as that drive you guys mentioned before, do they offer one for pre-alpha setups? 1.5 ratio?

Ayuh,.... The Alpha 1 is a direct bolt-on replacement for the MC-1 drives(what yer callin' a pre-alpha),....

So,... No need to change yer title, 'n Yes, an SEI will bolt right on, 'n go,....

The interchangeability ended in '91, with the Gen.II drives, as the shiftin' system changed,...

Would the SEI drive bolt right onto my gimbal? IE If I buy a complete alpha 1 upper and lower, would I need to change my trim cylinders, bellows, coupling, etc?

Nope,.... The Alpha 1s, 'n MC-1s are direct plug, 'n play swaps,....