I have an 88 Ford F150 that came from the factory with an AM radio. I have gone to the Wrecking yard and purchased a factory AM/FM Cass to install from a 91 Ford F150. I plug it in but can only get AM reception. I can see on the display that its on FM but still only AM stations any ideas

 

Unless you added an FM antenna, you're not going to receive much of anything on the FM band. AM antenna's are internal to the headunit, but FM is the 31" mast on the front fender with a coax wire that plugs into the round hole on the back of the radio. You can pick up antenna kits for under $20 from most places, just look at the size/application, newer chevy's and imports have odd connectors. Older vehicles and Fords use the standard size.