I've hit 50+ on that stretch many times, with several different bike computers... And you outweigh me by 20 pounds or so. It's certainly possible to go much faster on a bike. A friend of mine once hit 70+ going downhill through a tunnel in a peleton (obviously no wind and a vacuum effect with that many people involved!).
I've also hit 52+ on several other descents. To hit your max, try the eastside of Tioga Pass or Sagehen Summit (both on highway 120).