Thanks for the response. However, I found out when trying to solve a repair problem it helps to first read the directions. I found an old Mustang shop manual for a '68 Mustang that described in perfect detail how to remove the panel. Once all panel attaching screws have been removed, remove the access cover to the heater controls located immediately to the left of the panel. Then reach through the opening with your left hand and unscrew the speedometer cable from the panel. The panel can then be removed so that the three electrical cables may be disconnected from the panel. I still a little foolish about making such a fuss about a problem that really wasn't a problem. However, I've learned after destroying many parts on my Mustang projects when I wasn't sure of what I was doing that it's always better to reach out to my Mustang friends for advice.
Looks like you have the same Mustang addiction that I have. 2018 GT convertible with performance package, 2008 GT California Special convertible, '92 GT convertible, '72 Convertible (presently under restoration), '70 Mach 1 fast back, restored, 351 C engine., 2 '68 coupes (projects not started, and a '67 coupe waiting to be restored.
Always good to hear a WAR EAGLE, particularly from an unexpected source.