Asked before, searched and didn't find.
 

I am looking for the hole between the portion of the dash where the instruments go and underneath the dash. Any hole - I need to pass a single 16awg wire. I've been under there with a light, in the dark, looking for some place to pass a wire. I have also looked at photos of disassembled dashes in this forum, and have not found one with sufficient detail to show me what I'm looking for. My next move was going to play spaceman under the dash.

(You know - head against the pedals, butt up against the seat, feet resting on the seatback - just like an Apollo command module at lift-off.) :)

There are a few harnesses going through that area, just squeeze it through the grommet of one of those.

Have you tried removing a gauge? Start with the clock it is the easiest so you can push from the back on the speedo and you should be able to see in pretty well. There are some unfused wires so disconnect your battery before doing this.