Thanks guys, so I downloaded the wiring manual (former ERA Owner y'know) and determined that everything controlled by breaker #7 was dark. In the photo you can barely see #7. It is the third in line from the left. With some difficulty, I undid the retaining ring and pulled it out and disconnected it. Bench tested it for continuity, tested good, re-installed it, and the circuit started working

So I'm good for now. Don't know how I'd get to any of the breakers that are further down the line tho'. Hope I never need to.
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Exes: ERA #745, CAVGT #180, Kirkham KMP0268, SPF GT40P2306, '05 Ford GT #1605, Exact 008, Kirkham KMP0928