Mike the CI piercing I referenced is on the firewall, up and to the right of the heater box. No where near the brake booster. See the shiny silver relay to the left of the cowl air cleaner in this pic.
Look for a punctured mounting hole there. Also, if the car has a factory A/C suitcase on the firewall, it's not a COPO, regardless of which way the evaporator tubes bend. No solid lifter engines had A/C, even in the 396 L-78 variety. Let us know what you find.