I'm in the process of switching my alternator to an external voltage relay so the PCM isn't controlling my charging anymore.

I have a question for anyone who has done any mods underhood that needed an ignition source.

What is a good wire for ignition?

I know about a couple in the cab but wondered if anyone has used one in the engine bay.

I'm not yet at a point where I can have the batteries hooked up and forgot to find it before I tore everything apart.

Thanks