bbeasley, it's clear that you enjoy the group rides, which is fine, but don't mistake them for training for racing.
I'm not much further down the track than you. A bit older, a bit lighter, started racing last season as a 57 year-old. I could hang with the racers in group rides, tick along at 20 mph in my recovery zone, all that stuff. But the intensity of the races simply blew me away. It isn't the speed, it's the accelerations and the racing skills. Interval training is what you want, and (like AzT has said) practice in a racing environment.