no spark in start

If it cranks then the block is grounded, and the ignition is fine...... except the ECU is mounted on the apron, so the ECU has to be grounded to it, and the apron back to the battery. If the coil is firing with the spare D spinning it which is still controlled by the apron mounted ECU, then the ECU is working so is also grounded. The only thing not addressed is the ballast resistor during cranking, and
Dana67Dart is on the trail.