I'm no electrical guru, but what I would do is to disconnect all wires to the distributor. Then I'd run a single wire from the + side of the battery to the + terminal on the HEI. HEI's only require one hot wire to operate. See if it will start. If not, the problem is possibly in the HEI module. If it starts, the problem is in the MSD circuitry. I have never found a need for additional electronics when using an HEI on a street motor.