if its an early 8v box then you may need to change the driveshaft flanges to the 16v 100mm versions. this also means 'modifying' the gearbox casingI had to do this to get a mk1 box to fit
All MK2 1.8 gearboxes have the 100mm flanges on, even the drivers. MK1 1.8 may have 90mm flanges though