1970 Chevy El Camino No lights and car does nothing when I

Electrical problem
1970 Chevy El Camino V8 Two Wheel Drive Automatic

Hi,
I was working on the brake booster on my el camino and had to remove the main wiring harness to get at the e lower bolt. When I finished with everything I turned the key and nothing happened. I've checked the battery and main wiring harness plug and everything is fine. Oh, I also installed a new set of gauges that included a new voltage gauge. Any Ideas would be helpful.
Thanks,
Frank