Squareback vs round back alternator?

A common problem with all combinations is that the voltage regulator (Vreg) doesn't have a solid ground. Chrysler relied on just that sheet-metal screw into the body as a ground. It never hurts to run a dedicated ground wire from the case of the Vreg to a good ground point on the car. Few people today still have the old electro-magnetic Vreg. As posted, you can buy a new electronic regulator for the older alternator (round-back) which has 1 field terminal (the other terminal grounded). Some look like the OE rectangular box, while others are a thin chrome box. That is termed "high-side switching". You can probably still buy new brushes with insulators for the alternators. Worst-case, you could switch to a later square-back alternator which has 2 field terminals. Just ground one terminal to use with the high-side Vreg, or you can use a later "low-side switch" Vreg (triangular connector) but would also have to run an IGN wire to the alternator (other terminal). The square-back alternator was used a long time, at least until 1982 (my Dodge Aries), so will likely be available for a long time.