Keep this in mind: The minimum length of a McCauley metal prop for a C75 is 71". The Maximum length allowed for a C85 is also 71 inches. The likelihood that your prop would be suitable for both is slim at best.
Also, the extra baffling is not required on model C and CD Ercoupes. It is desirable, but very expensive. In addition to a new venturi the carb also requires a different main jet. Continental will not allow a model change unless the engine has been recently overhauled. Consult Continental bulletin M47-16 for the gory details. John Cooper Skyport Services 4996 Delaware Tnpk Rensselaerville, NY 12147 518 797-3064 www.skyportservices.net
