Found this.....
1987 Ford Mustang Light Bulb Fitment:
1987 Ford Mustang High & low beam headlight uses 9004 bulb.
1987 Ford Mustang Parking light uses 2357A bulb.
1987 Ford Mustang Front turn signal uses 2357A bulb.
1987 Ford Mustang Rear turn signal uses 1157 bulb.
1987 Ford Mustang Rear turn signal uses 1156 bulb.
1987 Ford Mustang Tail light uses 1157 bulb.
1987 Ford Mustang Stop light uses 1157 bulb.
1987 Ford Mustang High mount stop light uses 921 bulb.
1987 Ford Mustang High mount stop light uses 912 bulb.
1987 Ford Mustang License plate uses 168 bulb.
1987 Ford Mustang Back up light uses 1156 bulb.
1987 Ford Mustang Rear sidemarker uses 194 bulb.
1987 Ford Mustang Ash tray uses 1892 bulb.
1987 Ford Mustang Glove box uses 1816 bulb.
1987 Ford Mustang Map light uses 105 bulb.
1987 Ford Mustang Dome light uses 912 bulb.
1987 Ford Mustang Dome light uses 906 bulb.
1987 Ford Mustang Step/Courtesy light uses 906 bulb.
1987 Ford Mustang Step/Courtesy light uses 168 bulb.
1987 Ford Mustang Step/Courtesy light uses 89 bulb.
1987 Ford Mustang Trunk/Cargo area uses 89 bulb.
1987 Ford Mustang Under hood light uses 89 bulb.
1987 Ford Mustang Instrument-general uses 194 bulb.
1987 Ford Mustang Instrument-general uses 161 bulb.
1987 Ford Mustang Instrument-general uses 1892 bulb.
1987 Ford Mustang Instrument-general uses 1893 bulb.
1987 Ford Mustang Hi-beam indicator uses 194 bulb.
1987 Ford Mustang Seat belt indicator uses 194 bulb.
1987 Ford Mustang Brake warning uses 194 bulb.
1987 Ford Mustang Automatic transmission indicator uses 1893 bulb.
1987 Ford Mustang Directional signal indicator uses 194 bulb.
1987 Ford Mustang Radio dial uses 37 bulb.
1987 Ford Mustang Radio dial uses 1893 bulb.
1987 Ford Mustang Light Bulb Fitment:
1987 Ford Mustang High & low beam headlight uses 9004 bulb.
1987 Ford Mustang Parking light uses 2357A bulb.
1987 Ford Mustang Front turn signal uses 2357A bulb.
1987 Ford Mustang Rear turn signal uses 1157 bulb.
1987 Ford Mustang Rear turn signal uses 1156 bulb.
1987 Ford Mustang Tail light uses 1157 bulb.
1987 Ford Mustang Stop light uses 1157 bulb.
1987 Ford Mustang High mount stop light uses 921 bulb.
1987 Ford Mustang High mount stop light uses 912 bulb.
1987 Ford Mustang License plate uses 168 bulb.
1987 Ford Mustang Back up light uses 1156 bulb.
1987 Ford Mustang Rear sidemarker uses 194 bulb.
1987 Ford Mustang Ash tray uses 1892 bulb.
1987 Ford Mustang Glove box uses 1816 bulb.
1987 Ford Mustang Map light uses 105 bulb.
1987 Ford Mustang Dome light uses 912 bulb.
1987 Ford Mustang Dome light uses 906 bulb.
1987 Ford Mustang Step/Courtesy light uses 906 bulb.
1987 Ford Mustang Step/Courtesy light uses 168 bulb.
1987 Ford Mustang Step/Courtesy light uses 89 bulb.
1987 Ford Mustang Trunk/Cargo area uses 89 bulb.
1987 Ford Mustang Under hood light uses 89 bulb.
1987 Ford Mustang Instrument-general uses 194 bulb.
1987 Ford Mustang Instrument-general uses 161 bulb.
1987 Ford Mustang Instrument-general uses 1892 bulb.
1987 Ford Mustang Instrument-general uses 1893 bulb.
1987 Ford Mustang Hi-beam indicator uses 194 bulb.
1987 Ford Mustang Seat belt indicator uses 194 bulb.
1987 Ford Mustang Brake warning uses 194 bulb.
1987 Ford Mustang Automatic transmission indicator uses 1893 bulb.
1987 Ford Mustang Directional signal indicator uses 194 bulb.
1987 Ford Mustang Radio dial uses 37 bulb.
1987 Ford Mustang Radio dial uses 1893 bulb.