Mass Air. This means that the mass air sensor measures precisely, the actual air flow going into the engine. The mass air sensor does not care what modifications you have made to your engine such as camshafts and cylinder head modifications, it simply measures the airflow and tells the computer so that the computer can calculate how much fuel to add.

Speed density system in which the amount of air entering the engine is estimated based on several other inputs (such as manifold pressure). The estimate is based on assumptions about the engine in use, so engine mods are more likely to confuse a speed-density system than a MAF system. 1986-1988 5.0L Mustangs used speed-density systems (except 1988 cars destined for California, which used MAF).

i think the town car has the later but not sure