BB, I don't have wire diagram for a 65 / 66 so I can't give you wire colours . But the intent is to locate wire from stop light switch to taillights (this wire goes through your indicators switch in steering column then two wires to stop indicator bulbs) . Then locate the wire from reverse switch to reverse lights. At a convenient location
cut both wires and connect to the other wire. Stop light switch to reverse light wire going to boot. Reverse light switch join to old stop light wire to steering column.
When you change the wiring in the boot for reverse lights and stop /indicators as described.
When complete indicators will flash in reverse lights. When selecting reverse both reverse lights will work but indicators will still flash as they had when brakes were used.
Red lenses are now just tail / stop lights.