Next, we placed a large wooden block under the perch on the right-side axletube and another block under the left-side axletube where the perch used to be. Because of the one-inch difference in leaf-spring spacing between the A-Body and B-Body, we had to locate each of our new perches inward 1/2 inch on each side from the factory location. We placed a new perch between the left side axletube and the wooden block and positioned it 43 1/2 inches from the right-side perch. (Measuring from the inside edge of one perch to the outside edge of the other yields the same reading as measuring from center to center, and it's a lot easier.) Using wooden blocks or cinder blocks, and doing one perch at a time assures that the new perches will be angled at the same orientation around the axletube as the original ones. This way, the rear U-joint angle will remain the same when finished. We scribed the perch's location on the axletube and then welded it to the tube. Next, the right-side perch was removed, and the new one positioned 43 inches from our left-side perch, again using the wooden blocks. Once we marked its location, it too was welded on.
With our new perches properly positioned and welded in place, it was time to reassemble our axle. Upon completion of our rear axle swap, we had a pair of 14x5 1/2-inch Rallye wheels widened 2 1/2 inches to the inside. Then we mounted and balanced a pair of P245/60R14 tires on our new 14x8-inch wheels. They fit nicely within the narrow confines of the Dart wheelwells.
Although we chose to widen the Rallye wheels, the availability of aftermarket wheels is excellent these days. if we had chosen to go that route, we simply would have ordered wheels with the desired offset. If we were working with a Duster, Demon, Dart Sport, or a '67 through '69 Barracuda, the open rear wheelwells would have afforded more space, and the clearance wouldn't have been as much of an issue as on our Dart. Once the axle is installed, the rear U-joint angle should be checked with a driveshaft angle gauge.