My method for measuring my rear steer is to pull the tires and wheels off the car. Put the weight on the rear end with jack stands. Take plum bobs and hang them off of the front of the rotor. Measure from the string to one of the holes in the ladder bar bracket. Do that on both sides of the car and it will give you an idea if the rear end is pointing in one direction or the other. Or if the measurements are the same (within 1/16”) then it likely has no rear steer. This is just my method and others have their own way. Tim Mcamis has a good video on YouTube to watch for rear steer that may help. Only thing is, his cars are all tube chassis pro mod cars that are not unibodies. So I keep that in mind.