Query on wing mirrors for a P38

Guys,
Looking at replacing the wing mirrors simply because the outer covers are cracked etc. Have looked on ebay etc. Basically what's the difference between the 6pin, 10pin & 12pins one's advertised on ebay. How do I know which one's are for mine. I'm guessing the difference in pins is down to the fact that some rr's came with the dipping option when placed in reverse which i don't have.

Mine also change when headlights from the car behind hit the interior mirror.

With a bit of bodging you can use any of them but obviuosly a you'll be down features if you go for one with less pins than you've got. I replaced my 10 pin with a twelve pin by swapping over the plugs, ignoring the two wires i didn't have before.