1) I drive hillclimb and need as short as possible gearbox, this will also be too long but fuck it...real hillclimb transaxle gearboxes are 5000+EUR so forget it, 1.6 will be for sure better than current 2.0TS
2) you don't buy new diff...by adding/modifying limited slip disks you are getting %
e.g.1 two fully new disks will give you OEM 25%....after year of using this is coming down, majority of today driven difffs in old 75's is less than 10%
therefore this is something to be changed....more disks you have longer diff will last
e.g.2 I can get 40+% with three discs or with four discs...four fully new discs will give you even above 50%
50% I don't want....I'm aiming 40-42%
I bought discs here due to cheaper gearbox syncho ring...but you can find this is other stores for less money (e.g. 50-60EUR)
http://www.myalfa.eu/index.php?cat=c1272_MOUNTING-LIMITED-SLIP.html