After cross referencing the M550dX front bar part #31356798565 it turns out the following US models also use the same one
F06 650iX Grand Coupe
F07 550iX GT
This makes ordering the part easier since a US spec car is using it.
This website lists a bunch of cars that this bar supposedly fits. The interesting part about this is it lists the F07 535xi and 550xi Gran Turismo which according to realoem uses the same standard bar as the F10 535xi/550xi!
Using this site it makes it easier to cross reference part numbers with what cars it fits along with using realoem.com
As of now the M5 bar doesn't look too good because bmw seems to use specific part numbers that fit only Xdrive cars and different ones to fit the RWD models.
I might have to give the M550dX bar a go once i confirm Bmw actually tweaked that cars suspension.
After looking at that polish bmw parts site it seems like the M550dX front sway bar is used in the lower F07 models as a Msport package option. At this point I feel pretty confident that this bar will fit the 535/550xi but now the only question left is this an upgrade (stiffer/thicker bar) or just a different part number....