96 F-350 crossed jumper cables

Hi, my friend has a 96 F-350 with a 460 5-speed and they crossed the jumper cables trying to start it. It wouldn't start so I started testing and there was no fuel signal or spark signal. I replaced the computer and it runs great. But, when you turn the lights on the engine dies and restarts after turning the lights off. Also, the tach and odometer don't work but, the other gauges seem to work fine. Many thanks for any help.