no spark in start

You could get another battery and power the coil and the ECU from that. Jumper the negitave side if the stand alone battery to the body or block. Disconnect the feed to ecu from ballast resistor. Disconnect the coil plus wire.
Attach the plus side of the stand alone battery to the feed of the ECU and coil plus

You now have a dedicated power source to run the electronics, no voltage drop during cranking.