I have a feeling the number five might be a wire pulled from one of the other plugs. The engine was SC and might have a slightly modified harness due to aftermarket gauges or other parts.

Thanks for your help!

 

Slows2k, you can run an ap1 harness on an ap2 engine? Did not know that. I imagine most of the engine side of the harness is similar.

 

Yes, you can run a 00-05 engine harness with a 00 dash harness. The Drive by Wire 06 and later harnesses are completely different.