Both fit. With the large you will have the stem a little higher and a larger axel-to-crown distance. With the small you will not be able to set those parameters. People usually prefer the small.
I have an M3 with a FOX 40 RC2 and just got an integrated crown&stem at Go Ride (www.go-ride.com). Try giving then a call...
I have an M3 with a FOX 40 RC2 and just got an integrated crown&stem at Go Ride (www.go-ride.com). Try giving then a call...