I just realized that I couldn't add this option to my Tempest if I wanted to. I don't have a pic of my speedo, but its like this one:
https://www.ebay.ca/itm/1964-1965-19...oAAOSwPPZgJ2LL
It doesn't even have a hole to insert the light socket. And for sure not the little box with the red lens. I guess in this case I'd do the warning light to the left of the dash bezel.