If you stuck your head in the clock hole, you have a small head!
The access is really tough. You may have to remove the cover in the trunk and with another person fish wires to where you need them. Of course hooking a wire up back there is impossible. I have seen holes drilled with a long bit thru the cowl so that the back of the radio can be accessed.
You may be able to remove the radio and use a big half circle fishing tool to pull a wire thru the clock hole to the radio. Lots of stuff under the radio on later cars.