I have an "old" vintage mid 1970's Atlas Turntable and I need to know how to wire the bridge track using DCC. Does it need an autoreversing unit or not?
No. The Atlas H0 turntable is an evergreen for the model railroad hobby. It was easy to install and simple to wire, making it quite popular.
Power is fed to the turntable bridge by connecting the track power feeds (black and red) individually to two screw terminals; these terminals are built into the portion of the Atlas turntable base which also includes the turntable manual crank handle. The turntable itself is internally wired so that the bridge track polarity is swapped when the bridge rotates and aligns with some of the tracks. One set of track connections of the turntable are marked with an "A" in the alignment slots of the base. The balance are marked with a "B", indicating that the rail polarity of the turntable bridge has been reversed for the track which is located for that slot.
DCC power is not DC but waveform AC, but you are still concerned that the power connections be properly aligned because of electrical "phase". Since the Atlas turntable handles the alignment of the rails, both physically and electrically, connecting an autoreverse unit to the turntable bridge is not absolutely necessary as long as you keep the proper power orientation to the various tracks served by the table.
If you are unsure as to the proper orientation for a specific storage track, you can determine the correct rail power orientation by initially using an ohmmeter to test continuity. Connecting one ohmmeter lead to one of the feed terminals of the turntable, you can then align the turntable to a specific track. Touching the other lead to one turntable rail or the other, you can determine which "color" should be connected to the same rail of the storage track. Or, you can connect an AR1 to the turntable bridge and be done with it.