OK then, how about this?
There seems to be 2 styles of alt produced in the late 60's - 1970. One has 3 contacts, output, field and a floating ground in an insulated brush holder. The other has 2 contacts as the ground (brush) is grounded by its mounting screw and has no spade lug.
Is the difference simply between the solid state voltage regulator type and the mechanical voltage regulator type?
Russ