Just got caught in major rain, no power after I turned car off

Sorry, thought it appeared in my signature, it's a '69 Dart. The issue I will be running into, is it is fairly modified from what it was stock (Magnum swap, battery relocated, etc), so any factory wiring diagram may not apply to mine. I believe the first thing I'll check for it a fuse in the battery cable, then the bulkhead. I've never had any electrical issues with the car, so I don't believe it has been caused by poor work or just a random coincedence, I definitely think the rain water shorted something out. The confusing part for me is what happened when I shut the car off to cause the issue. I wish I had paid attention to whether the dome light came on after I turned the car off, but it was still light enough outside that I didn't notice.