The 5 speed gearboxes are the same for all 131?s and 132?s I think. The only difference is that on later cars the 5th gear is 0.83:1 instead of earlier 0.87:1, just a little bit taller.
no - some early cars had the colloti (124/125 type) gearbox, later cars had the ZF gearbox which is stronger, and that also came with two different rear output styles. Not sure on all the ratio differences but most of the differences would be between the different boxes rather than different ratios in the same box. e.g. all 2 litre manual cars had the same ratios as far as I know (131 or 132/argenta)