If you're looking for one for towing, any 2001+ will have the better PI version of the Romeo 4.6 2V mod motor. In the police interceptor, this is rated 250 HP and 297 ft lb torque (PI means Performance improved, Windsor engines got it in 1999 and the Romeo engines in 2001).
An old Police Interceptor will probably be most capable of towing and a lot of these can be had with the receivers already installed.
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1988 9C1 - Modified LM1 @ 275HP/350TQ - TH700R4 - 3.08 8.5" Disc Rear - see it at
http://www.silicon212.org/9c1!
2005 Crown Vic P71 - former AZ DPS - 4.6 liters of pure creamy slothness!
1967 El Camino L79/M20 old school asphalt raper
Remember - a government that is strong enough to give you everything you need, is also strong enough to take everything you have.