73 dart front brakes

If your car is a 1973 model, I do not believe that it would have come from the factory with an 8-3/4" axle. The disc brake cars were equipped with a 4.5" bolt circle while all of the drum brake cars were equipped with a 4" BC until 1976. The only way that you could have a 4" BC is if your car was originally equipped with drum brakes and, at some point, someone converted the fronts to discs.

Chances are that you either have an 8-1/4" axle or a 7-1/4" axle. Both of these axles have rear covers with either 10 bolt or 9 bolts respectively. The 8-3/4" axle has no rear cover and bolts that secure the ring & pinion assembly to the axle face the front of the car.

If you really have the 8-3/4" axle, you can redrill the axle flange and brake drum but this means that replacement drums must also be drilled to the 4.5" BC. Another way to change the bolt pattern is to replace the A-body's 9"x2" or 10"x1¾" rear brakes with 10"x2½" or 11"x2½" brake drums and backing plates from a B or C-body car and order new axle shafts from Moser to suit the larger bolt pattern and rear brakes.

The third option is to replace the axle completely with one from a F or B-body car. In this case, the spring perches would have to be relocated to the A-body locations. While the axles are wider (flange to flange) than the stock width of the A-body axle, the difference will be relatively small once if compare it with the the width of the A-body axle with upgraded 2.5" wide brakes. This option will also bring the track of the rear tires more in line with those of the front tires.

Frank