My moms 73 dodge dart was the same way, wider in the front track than the rear. I have no idea why it was done. In the case of my nova it actually hurt interchange of drum to drum rear axle assembly's with second generation Camaros made at the same time. Hard to believe today that 3.73 was a "economy " ratio used on a car without overdrive. To your knowledge when did Chevy quit using those tags? Jay
