The 711 speedo is the exact one you need! No problems there.
It looks like a good bike just as it sits - I'd have touched it up and ridden it.
I've also gotten these bikes with cracked discs - they seemed to work ok for the PO that way, but just a bit too spooky for me.
Wanted: Dead, smashed, crashed or trashed gauges
BMW GAUGE REPAIRS - TACH*SPEEDO*CLOCK*VOLT METER *PODs & LIGHT BOARD*