Considering that the full framed Crown Victoria without the factory towing package was rated for 2,000 pounds, I would guess that you would be looking at 1,000, or maybe 1,500 pounds tops. Don't forget, you are looking at an engine that, in factory trim, was putting out roughly 100 horsepower. Not very much at all. Plus it is a unibody car, so I would be very leery towing at all with one that is that age now.
The thinking is having the ability to pull a rental trailer for the occasional item that is too big to fit in the back such as an organ console (yes that is the kind of thing that I would want to carry on occasion). So a payload of maybe 1000lbs but usually less plus the weight of the trailer. Possibly a small travel trailer. mike
I would look for a Colony Part or Country Squire for sure, and find one with the factory Trailer Tow III package. With the 302, that gives a factory rating of 5,000 pounds. IF you are super lucky, you'll find one with the 351W as well, and that gives a tow rating of 6,000. Either way, the tow package is the way to go. You can tell quickly because the tow package cars were equipped with a power steering cooler as well as an external transmission cooler. They also had heavier single rate springs and shocks all the way around. On the wagons, the front anti-sway bar is upgraded. On sedans, they came with the upgraded front, plus a heavy rear anti-sway bar as well. The wiring is also done at the factory for all 7 leads, and the lights run off relays in the left rear quarter to protect the wiring of the car from any problems.
I'm having a hard time finding a hitch for mine. I would like to pull a small boat with it. StorminNorman has a hitch but it was installed in Mexico. He hauled a huge trailer load of stuff from Mexico to Canada. I'm sure it was well-overloaded, but his car still seems to be intact.