If installed backward the axle would be so far out of location you wouldnt even get it back in car, the center would be almost to the center of the gas tank.Mopars do not locate their axles on the center of the leaf springs.
Measure from the front spindle to the center line of the rear axle and compare the dimensions.
Also older cars were built with larger tolerances, meaning that the stackup of plus or minus tolerances will create differences similar to what you have. Has the car been restored?
Nice looking car.