WCAU was not a Top 40 station.
IIRC, WIBG was the big Top 40 station in Philly back then. Not as big a signal as KYW or WCAU, but they were a semi-regular in Indiana when I lived there.
And you forget the great voice of the Plains and eastern Rockies, KOMA in Oklahoma City which may well have been the most listened to station in America during the late 50s and 60's.
Don't forget "K-Double A-Y" Little Rock. I could hear both of them loud and clear in Indy, Chicago, and Phoenix.