just fit the 1.9 rear, job done

1.6 has a shorter ratio box, i use one on 205,

gti6 brakes are a good upgrade, but as you have a 1.6 they wont fit, so you either need the 306 gti6 hubs or a set from a 1.9 gti

if you do this you will also need 1.9 drive shafts