Spacer plate in front of leaf spring hanger

My Dart has never been wrecked and so it was not a case of putting the car back square from a tweeked chassis. The part that befuddles me is that this plate was only present on the drivers side which goes against the idea that it was done to put bigger tires in the rear. I can only assume that the plate was installed at some point in her life to square up the rear end with the front end. At the moment, she is getting a new paint job and so when I get her back, I will string the sides to see how far out of square she is and then put the smallest plate possible in to correct the difference. I am new to the Mopar and leaf spring game, so I may need to consider moving both sides back a little to get bigger tires in there as currently she is riding on the original 14" Rally rims and I am not planning on keeping those.