70/71 are specific units, being still roundback like earliers but both brushes isolated ready for electronic regulator like squarebacks (they began on 72)
They look exactly like this
HOWEVER, if you want to make the propper investment and not looking for a “correct resto job matching numbers for a trailer Queen”, but enjoy the car, get a more powerful unit (no matter if you car is non A/C, but still with the heater blower) able to source no less than 45-50 amps at iddle.
There IS NO factory alternator up to late 70s or 80s, able to feed that. You can get aftermarket HiPo units (95-100 amps) on US$200-250 rate (still being roundback and ready with isolated brushes) or get an 80s 78/80 Amps alt which are squareback revised versions (a bit wider than the first version) on $70-100 rate from parts dealers. These are couple of millimeters wider and depending on engine setup, fitment can be a deal to deal with (BTDT). These are also tipically fitted with a smaller pulley which makes to give us more juice (or sooner into the RPMs curve) from it.
Some other option is the NipponDenso units, which are tipically on 60 amps max output rate BUT way better iddle rate than factory Mopar units (this is due the diff stator winding design). These require a diff bracket setup thought (available around from several dealers offering the conversion)
I allways advice NO MATTER THE CAR, YEAR OR ACCs, our cars require NO LESS than 45 amps alt capability at iddle. Remember alt will provide the juice requested for, having a 300 amps alt doesn’t mean will provide 300 amps. Just IS ABLE to do it if requested.
Having the source able to feed any requested power from the car at any engine speed will get you on a RELAXED charging system, STILL on original wiring since a discharged battery won’t be anymore a problem which will increase the power demand constantly.
(Although a small wiring upgrade is good)
