Biba, US market gtv6s came with two mirrors (that didnīt happen on European versions, I can recall from pics that later gtv6s did) so your switch must have the "toggle/rocker switch used to change from side to side". I assume that it is the same as the spider switch.
My 82 alfetta-gtv (Euro version) came with only the driverīs power mirror, with one joy-stick switch located at the console, almost at the end (same location as gtv6). I bought a second hand RHD mirror by the BB, and found an alfetta-gtv switch in England, so I stayed with my original switch for the LHD and installed the "new" one at the console, below the original switch. It is great!!
Sorry, but I donīt know a damn thing about electrical stuff, and as labour in Peru is cheap I had a guy wire the switch & mirror, I can recall they used two relays.
Unfortunately for me, the motor in the mirror didnīt work, Iīve sourced one now from a BMW e30,(e36 also is the same)

. But someone stole the mirror glass!!! I donīt know why since alfas are very rare here, it will not be useful for another car, down here they steal those things always. Fortunately I bought a glass through the BB and I am just waiting for my friend to bring it here.
As the location goes, the one on the gtv6 is not the best, as you may touch the joy-stick and the mirrors would move (it is weird that the original joystick has direct power from the battery and not from the ignition, I will have to fix this). So if you may find a location where they will not be hit, it would be great.