Installed msd ignition box and dizzy. Now wires under dash try to get hot

You can troubleshoot this by putting a large wattage bulb in series with the battery ground, such as an 1157 turn filament, or 1156 back up lamp

Turn on the ignition and pull fuses and disconnect components until the bulb goes dimmer. Unplug the VR and unhook the alternator

WHERE EXACTLY did you hook power for the MSD?