I just did this it and it was cake. I don't have a dead pedal. I'm 6'2 with size 13 shoes so my leg goes all the way to the back wall, which basically IS my dead pedal. I ended up mounting the switch to the back of the footbox just left of the clutch pedal arm, about 10 inches from the floor. It just clears the arm with the pedal fully depressed, and there's still room for my foot to the left of it. I used a Ford high beam swtich from NAPA that was made in Taiwan.
Wiring it was simple, but I'm not sure what setup you have - carb or EFI. I have EFI and I simply probed the back of the Mustang turn signal assembly to figure out how the stock switch works and what wires go where. There's a hot lead into the switch from the factory headlight switch.
The high beam switch simply toggles the power between the two outputs, one is connected to the high beams and the other to the low beams. The two are never energized at the same time.
I think there's a post in the Engineer Ed column on the subject that might help you further.
Sorry I don't have any fabrication advice or pics. I considered this avenue, but later changed my mind because there just isn't enough room down there for my feet, let alone a dead pedal with integrated high beam switch!