omc/mercruiser compatibility

[EdBence]

Hi I have a sonny Levi Delta 25 which I put together a few years ago from Mercruiser bits, a new 5.7v8 on an alpha 1. I was never able to connect the through hull exhaust as the engine mounts on the bell housing were too wide to fit the cowhorn. I think the bell housing and transom plate came off an old 888 engine. I am fed up with the noise of a through hull exhaust and have been exploring ways of sorting this out. I have managed to get an omc bell housing and transom plate which will fit the cowhorn but before I pull the engine does anyone know if the bolt pattern on the omc inner transom plate will align with an alpha 1 they look very similar thanks. Ed