hi there, i am wanting to convert my 1990 subaru legacy gt from auto to
manual, it has an ej20 single turbo in it. I want to put in a gearbox from a
later model twin turbo ej20 legacy or forrester perhaps, but i was told that
the bellhousing bolt holes would not match up. I am aware that i will need to
fabricate a rear crossmember for it but is this true? and what is the reson
for the bellhousing to be different it does not make any sense?

The bolt hole should be the same as they are the same blocks i cant see a problem