The pre 70s ground one terminal of the field at the alternator.
The 70s and newer do not have the one field terminal grounded as the voltage regulator provides a variable ground to control output.
A 70s and newer alternator can be easily adapted to work with a pre 70s charging system by simply grounding one field terminal. So if someone is selling an alternator to work on both systems they are likely providing a short ground strap or wire with instructions.
MOPARTS ALERT!: Chris Pugh aka gabodyman of Dalton, Georgia, cashed my $140 money order on 4-16-02 never sent parts. On 3-19-07 he agreed to return my money; "april 9, it will be in the mail by that date""will do as promised. chris" Still no parts and no money!
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