I thought the 1.8 had the ib5 gearbox which is like chocolate, the 2.0l which includes the Mk1 foucs RS has a MTX75. They are not interchangable as far as im aware. If you go to the trouble of fitting a 2.0L block then i would fit a Getrag 6 Speed box from the ST170, with enough horses they have a theoretical top speed of 180+