Just as an FYI there was an A65 Continental, but no C65...
There
were both A75 and a C75s... The A75 was basically an A65 that revved higher. The C75 made its power through larger displacement instead. There was also an A80, which was an A75 with higher compression ratio. Quite confusing!
Good luck finding a good A65 for the Collegiate! I think it'll be much better than the A50. Its a cool plane.