Looking in the 1966 Chrysler factory service manual (as representative of '65-'68 C-bodies), that bulb number is "1816". Looking in the 1970 Chrysler factory service manual (representative for '69-'73 C-bodies), that bulb number is "330". Two completely different bulbs and related sockets, it appears. Not sure about '74-'78 C-bodies. A Google search using those bulb numbers (as bulb 1816) can bring up many places to buy them, in name brands.
To verify for your vehicle, you can look in the "Specifications" section of the Owner's Manual.
Just some thoughts,
CBODY67