"There was sufficient material to lock vice grips on the bolt and while applying heat from a propane torch (careful it's only aluminum) and tapping I attempted to loosen her up.... hmmmnnn... soft bolt, I keep mangling the material; no joy."

Well For one, using the vice grips was a bad choice. A longer extension on the ratchet may have helped. It looks to me like a 6 sided bolt.
Maybe the bolt just got stressed from heat?