[strictlypersonl]

Which connection depends on how much load you are expecting and whether you want the plug switched with the ignition. There is a brown wire (#30) near the firewall that is switched (originates at the top fuse on the driver's side) and capable of 10A. More switched current than that would come off the ignition ACC terminal.

Unswitched can come off of the Stewart Warner ammeter or at the ignition switch. You'd need a fuse for either of those taps.