I believe SEI has one that convert to an Alpha GenII. Could be bad memory, you’d have to double check.

I did an omc to bravo swap on a chris craft 245 limited last year and it was all literally plug and play. I didn't have to move anything or even drill a hole. I was very surprised at the ease of doing the whole job. That was big block chevy application though.

Yes, they do make a retrofit bell housing. But that is cobra to alpha. This is King cobra being changed to bravo.

One thing I have found out that I guess is a good thing, is that the yoke that goes into the coupler is 100% the exact same part for OMC and Bravo so that will at least not be an issue.

What if you use the omc inner transom plate and bell housing with the bravo transom assembly?

Saw your post and just came across this

https://www.sterndrives.com/omc_to_mercruiser.html

Yes, I have done this swap using a donor boat. That is what you need to do, reusing the old inner plate, It bolts up fine. I believe they were both1990 era boats. I didn't have a bravo bellhousing to use. I had to swap controls also FYI.