I put some Bridgestone Spitfire S11s on a K75S that I brought back to life last year. I rode the bike to Sacramento down The Cascades and they seemed to perform just fine.
Personally though, for riding hard, I'd be tempted to try some off-size radials that will fit those rims. I'd go with a 110/80-18 Bridgestone BT-023 or Pilot Road 2 on the front and a 140/80-17 Avon Azaro AV46 on the rear.