The 510 uses an R160 rear diff, there are some replacement options for that
diff or even going to an R180 is possible, to go the R200 way you will need some work done to clear the hinderence between the diff and the spare tire
wall.
As I see it, the 510 is getting more attention these days among our local
community, perhaps we need a "510 only" topic started to share our common passion for this car. I am a 510 owner myself, I actually own 2 of these.