Mike, I know I'm late on this reply, but did you find your problem. I just had the same exact problem and there was an open behind my fuse block. I think it was the splice in the service manual called S200. It gets power from fusible link "A" and then distributes it to the fuse block, horn, and a few other things I can't remember. Any way, I had headlights and interior dome lights, but not much else, including a dead ignition switch. I disco'd the fuse block from the firewall and as soon as I pulled it back, all the lights and bells fired up. Let me know what you found and if it was an open wire behind your fuse block, how'd you fix it?
Thanks, Mike.