Lights Problem...

[WRKTRUK]

I have a 1984 C-10 Longbed, completely stock wiring wise, but with a 355 in it to keep up with the Mustang GT's on the interestate. Anyway to the topic at hand, last week as I left work I turned the lights on and when I did a blue spark went across the lower dash (metal part) right at the headlight pull switch. Well at that time my gauge cluster lights and tail lights immediately quit working. My interior dome lights come on when I turn my head lights on, but are very dim and brighten up when I shut them off, but the interior lights are ALWAYS on now unless the truck is off. 1st thing done with no testing was I replaced the head light switch, well that didn't change a thing. I checked and replaced any and every fuse that even remotely looked bad, still nothing. Well last resort I have another gauge cluster out of an 85 truck that I know works so I plugged it in and STILL nothing different. So here I am looking into the vast amount of knowledge on this site to direct me where to look next, or what to test/replace next. I have searched the electrical section with nothing but questions about 67-72 truck problems, so hopefully this section will get me the feed back I need.

Thanks in advance,
Ryan

Oh yeah, last thing the stuff that works fine is the headlights both bright and dim, the blinkers both inside and outside front and rear (including the green lights in the cluster), and the Blue lights in the cluster indicating that the bright light are on.