As a former C309 owner, here's my experience -
The winches are through bolted. The port bolts are easily accessible in the cockpit locker. The starboard side is harder, requiring the removal of the trim strip in the aft cabin (4 screws) and then reaching around the lip of the headliner. Harder still if you don't have small hands. If you try to disassemble on the boat, you will find that the lower gear cannot be removed due to the way the winch base is recessed into the coaming. Obviously not a problem on the cabin top winches. I would not, however, recommend unbolting and removing the winches since you will likely have problems breaking the thick bedding, and will then have a real bear of a job rebedding them, and especially getting a wrench on the starboard winch bolts to tighten them. It only takes 15-20 minutes to tear down, clean, lube, and reassemble a winch in place.