I think I found a supplier who can make LSD for 300 series diff.
I have a photo for a different car but you get an idea.

I think it will be about £600 each or less.
Let me know if any of you are interested so that we can get better discount.
Also, can anyone tell me if all of diffs are same in both 340 and 360 gearbox?
Cheers
Atchi