Fan,
To be precise that is not a C model.
Fibreglass TR blades like a 300 means C-18 engine.
The "C" has metal cambered TR blades (Frank Robinson?) and normally a C-20 engine although early ones had C-18's. The "C" frame had a 3 cluster instrument panel as the engine oil pressure gauge was changed to a separate instrument. Older aircraft could be upgraded by fitting the cambered TR blades, and using the "C" flight manual with appropriate data for the engine installed.