Here's a site that you probably already know about, Reel Radio,
http://www.reelradio.com but for those who don't know about it, people can send in airchecks they have of Top 40 stations from the 50's thru maybe the mid-70's or so. You need to make a donation that lasts a year to listen, I think it starts around $15. No WHLO, but there's some WHK, KYW, WKYC, WIXY, WJW (Alan Freed and Mad Daddy), and quite a few CKLW airchecks. Don't need to join to search. Some checks are scoped, some unscoped.
And if you contribute several airchecks, jingle reels, commercials, etc... to reelradio, I believe that any future membership renewals are waived.
I have a few older things from the 60s and some from the 80s that someday I will get around to sending to Uncle Ricky @ reelradio.com.