Where are the spark plugs located on a 1991 Lincoln Town Car?

The spark plugs on a 1991 Lincoln Town Car are located on top of the engine, within the valve covers. Because it's a V8 engine, there will be eight spark plugs, four on each side of the engine. To access them, you'll need to remove the valve covers. This requires removing the air cleaner assembly and possibly some other components depending on the specific engine (it would be a 4.6L or a 5.0L). A repair manual specific to your car's engine would be very helpful in showing the exact location and removal procedure.