Increasing Mercury Marquis towing capacity

I’ve seen it done, but most of these had a special trailer towing package installed. This included HD transmission with HD radiator, HD springs and a performance axle.

I had such a package on my 1984 Chevy Impala which raised the towing to 5000 lbs I believe.

You could install a transmission cooler and make sure you have electric brakes on the trailer as well as a load distribution hitch. And keep the car out of overdrive.

If you can find a used Crown Victoria police cruiser it would have all this stuff already installed. They make good tow vehicles.