[Depends, are the switches turning on RELAYS or the LOADS directly? If the switches are merely turning on relays, there's no need to use a relay to feed the switches.

Frankly, the BEST way to feed a buss for all big loads, fans, stereo, etc, is probably to get a "continuous duty solenoid" and turn it on off the ignition, then feed everything else off that.

The problem with adding stuff on these cars is several:

The ignition switch and connector has it's limits

The bulkhead connector is a problem

The wiring is not large enough

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It appears I need a "big" relay to do the switching but after that I was hoping to switch direct to Pump and fans, etc. I have some high amperage military switches that should last forever. The battery is in the trunk so I will either run a 6 awg from the trunk to under the dash OR, as recommended, grab and run a shorter wire from the Starter Relay to power up the High current side of the Relay.

A big solenoid. Hmm, I wonder if you can keep a Starter relay energized? I bet it wasn't designed for continuous power. I have a Ford Starter relay kicking around, I think I'll throw 12 volts on that and see how hot it gets.