Anything that uses more than 10 amps gets properly fused and has relays installed on the circuit. I power the relays through a 12V+ distribution lug located in the engine compartment, and that is often the starter relay lug. Of course, the typically 4 gauge cable from the starter relay to the battery continues the current flow from the alternator to the battery.
JBC, this is what I'd like to do, also, except for this; if I've read correctly, running a 12V+ distribution lug off the starter relay lug would mean you're powering these off the battery, and what I've read is that you need to power any added accessories off the alternator, so that you're not discharging the battery any further. I'm not talking about anything factory, like factory radio. Instead, I'm thinking aftermarket stereo amp, a light bar, a CB radio, a power/USB plug. Also not talking about a HEAVY draw item like an add-on, non-PTO winch ( I see where many folks run a 2nd battery under the hood for something like running winches or electric plows).
On this '73, the PO had the truck for probably 30+ years. It ran a plow. He was a mchinist by trade, and built his own Holmes wrecker boom for this 3/4 ton truck. He put another relay next to the starter relay on the fender, and ran a power wire from the starter relay stud to this new relay to power it. This would have been powering it on the battery side, if I follow correctly. From this new relay, he powered the big winch that ran his wrecker boom, and also his plow. Given the high draw, that makes sense to me to power it that way, off the battery. I'm not running either of those on this truck now, and have removed that relay and wiring.
