Yes, Jaco and Alfred are correct, the earlier cars had a straight-edged firewall ridge and no access hole. Mine started off that way but was "modified" by some overzealous mechanic along the way. He took the liberty to gouge a hole to get to the heater valve. This was the olden days before I subjected mechanics to an FBI background check! I did not notice it until I replaced the padding in 1999. Anyway, I used my tin snips to cut a much rounder hole and stuck an access plug in it. Made the best of the situation...