8 3/4 axle problems

I need advice!

Changed axles in 1968 Dart GTS back to the original 4" bolt pattern. Replaced all seals & bearings with Federal Mogul parts. When I bolt the left axle in I have no end play at all. If I put the other axle back in which was 4 1/2" bolt pattern, it is fine with end play and I'm able to use the adjuster on right side. Even without the right axle in the car, the left side has no play.

Axles measure the same and look identical except the bolt pattern.
Thanks