Almost nothing is available reproduction for the 67 Coronets. Most difficult to find trim is the grille surround moldings. If the grille surround moldings are not salvageable on the car you're looking at, you could easilly spend over $1000 for good used replacements.
These are just the trim pieces that wrap around the grille. They always get damaged at the leading edges of the front fenders.
There may be small patch panels for exterior sheet metal available, but I don't know what the quality is. There are no quarter skins available other than the 66-67 Charger quarter skins, but they have different rear wheel openings. Floor pans, and I believe trunk floors are available.
Common rust areas, on a 67 B-body convertible is in front of each rear wheel well, and everywhere else a 67 B-body rusts. Check the entire lower half of the car carefully, including frame rails.
Front fenders are basically the same for all 66-67 Coronets and Chargers except for headlight mounting points. Hoods are also the same for 66-67 Coronets and Chargers. Doors for 2 door models are the same for 66-67 Coronets, Chargers, Belvederes and Satellites, but convertable doors have different glass and have additional parts mounted on the doors and door jams to reduce flex in the body (don't know what thos pieces are called).
Front bumper is unique to 67 Coronet. Rear bumper is shared with 66-67 Charger.
Interior rear quarter molded plastic panels are difficult to find unless someone is reproducing them that I don't know about. I think someone is now reproducing the convertible top latches. Make sure the top frame is solid. I had a parts car convertible once that had parts of the convertible top frame rusted out.
Make sure all convertible specific trim glass and hardware is there as they will be difficult pieces to find.