FWIW, my 80s sit under these (keeps them reasonably dry in the heaviest rain - but I don't live in the PNW):
and when they don't, I have custom cut magnetic vinyl over the cowl panel to keep the leaves out:
Damn!
You have your work cut out for you. At this point, if it was me, I'd get an EWD, start at the battery and work my way to the ends of the engine harness. After you get through there, and only then, start on the A/C circuit.
There is a temp switch in the DS side of the head, which cuts...