440six,
I did some more looking and I found one picture in the Barracuda Challenger source book, it is of a 1970 non-rallye dash and it shows the road lamp switch mounted under and slightly to the right of the dimmer switch, similar to your latest post. This is from a copy of the 1970 Barracuda sales brouchure, and its not a very clear picture.
I also looked through other pictures of cars that I have, and I found 2 with road lamps, they are not very good, one is of a 1970 AAR Cuda with a Rallye dash and the switch is mounted like the picture I posted, the other is of a 1971 Cuda with a non rallye IP and the switch is also mounted low. I'm am not sure if these 2 cars are factory locations.
I keep looking into this and let you know if I come up with anything.