How much is a Mustang rated to pull?

Mexican road train. They don't have body damage but the fender covers have been removed to attach tow bars. They leave the engines running with the car in neutral to save the automatic transmission from damage on cars where removing the drive shaft(s) is difficult (especially front wheel drive vehicles). Sometimes, the last car will have someone sitting in the drivers seat to apply brakes. Usually, these Mexican road trains travel at night to avoid law enforcement.