The three wires sound like an external coil. Did they use external coils on a V8? The external coil on my six has three wires (org, blk, brn) that exit the body from under the cap and go to an external coil. They only made the external coil for the sixes for two years 74 and 75.
Now if it has the "nub" with Bat and Tach on it, like Stuart says it is coil in cap.
HEIs don't require any maintenance to speak of. About all there is to do is check the bushings on the centrifugal weights.
Larry
