The bulk of the ads (and, I assume, most of the extant 124s) are in California, a land better wired than most, so the sample is heavily loaded towards the West Coast.
Useful classified ad sites include www.recycler.com, www.adone.com, and the want ad sections of the San Francisco Examiner, the San Jose Mercury News, the Houston Chronicle, the Virginia Pilot, The Raleigh, NC paper, New Jersey's Star-Ledger and Asbury Park Press, Special Cars Journal, Autoweek, and many, many more. If you even want to test your wits against Yahoo, Alta Vista, or the Open Text search engines, try finding pertinent Fiat citations without involving yourself in Italian television, the Catholic Church, or Ansel Adams' work.