I have replaced all the harnesses in my 69 and find it invaluable. I actually just put in a new front headlight wiring harness and engine harness the other day. Connected everything up and plugged them both into firewall. Went to turn key and nothing - no interior lights, no ignition, nothing. Totally bummed I checked all my connections by referencing the diagram. Still nothing. Unplugged the harnesses from the firewall and viola! The main power lead's (big fat black and red wire)terminal was bent flat - thus not going into the fuse box. Straightened it out and plugged it back in and it fired right up and all lights/ horns/ signals are working as well. Good luck - I hate electrical issues
