Is the Mallory Unilite electronic distributor supposed to get a full 12v or 8v that would come through the resistor wire?

Any changes made to the starter wiring? Are the starter wires wired to the correct "S" and "R" Terminals?

Has the ignition switch ever been changed?

You should get a full 12v while cranking from the purple wire and a constant 8 volts from the pink resistor wire. So as BronzeBird said try a direct wire from the battery to the coil and see what happens first..