V8 into a 1984 90

Hi just brought a V8 which was fitted into a 90 as standard but it didnt come with a gear box i want to fit it into my 90 which had a 2.5 petrol engine fitted before i have seen some where the engine is tight upagainst the bulk head and some which have loads of room behind the engine but is close to the rad, will this engine fit straight on to my gear box or will i need to get a conversion ring or will i need to fit a RR gear box,
Thanks

didnt i answer this somewhere before?

Yes you did thanks just thought i would ask in section as i am new to all this