Bellhousings

[chassis 33]

I posted this over in Engines and Drivetrain but no-one seems to know.

Does anyone know a)what spec gearbox is in my 1989 e30 318i with an M40 engine or how i can find out what gearbox is fitted, also b) what engines other BMW engines mate directly to the bellhousing? I think the M42 318is engine will work any others? Thanks in advance.

Regards
Iain