[Ultra89Rider]

I have seen Aftermarket Electronic speedometers that have pick ups mounted on the rear axle.

You can not add a factory pick up unless you change the transmission to a FLHR transmission. The trouble with that is the oil tank is mounted below the transmission. This will not work on any FXR with out major modifications to the frame. (ie..brake master cylinder relocation)

 

[Ultra89Rider]

You could change engine cases to an aftermarket FXR case, like one from STD.
Ed

Don't you mean "The Transmission" Case? The engine case does not have anything to do with the Speedometer.