It's pretty rare that this is done, the modification is usually the other way around, putting a "square back" in an earlier rig with a "round back" with the press in diodes, a pain in the you know what alternator to work on compared to the square back...

"Chrysler retained the "B" circuit, single field wiring design through the 1969 model year. In 1970 electronics were starting to come into their own and we started to see the electronic voltage regulator. When Chrysler went to the electronic voltage regulator the wiring design changed from the single field "B" circuit to the double field "A" circuit, which now had two field terminals on the back of the alternator. The frame design stayed the same and another terminal was added for the second field. This style alternator stayed in production through the 1971 model year. For 1972 Chrysler redesigned the alternator. The front frame stayed the same, but the rear frame changed considerably. Instead of the can type pressed-in diodes used in the earlier alternators, they now had a positive rectifier and a negative rectifier each containing the three diodes. These were bolted to the rear frame as two separate assemblies which made a common electrical connection that the stator windings also connected to. This style of alternator greatly improved the repair aspect as no soldering was needed to join all of the diodes and stator windings."