3 piece shaft dont do this!! But good drivers skills will Use "that" weight transfer to your advantage.

You will have to be pushing sum serious power.... which i know your car and my own car is not pulling To have the need for a LSD (If you have 3 piece)

If it fails after having 3 piece shafts you can always pay the extra and get the diff, but you wont need it .

Its oviously different for your setup as you have the diff already, but that dont matter. Even YOUR car will benifit from the 3 piece shaft setup

HTH
Regards
Jano