Perhaps the lesser models without the full door trims don't have the hole. I havent taken much notice of them either. My GXL has the inner hole on the left (but you need another hole under the mirror for the cable). I have seen GXLs with left and right but I am told they didnt come like that. I tried to fit a LH mirror to mine only to find the handle ends up upside down, You need a special LH mirror CABLE even though the glasses interchange. Thats unless you are prepared to put up with the mirror going the opposite way to the handle. IMO you are wasting your time. I have a brand new one in my drivers door, and even new they are pretty useless. Limited travel and you feel like you are going to break the little handle everytime you use it. Or bump it with your leg getting in or out and snap it clean off which I have done a couple of times.
1978 XC Fairmont GXL, Emerald green, Jade Int. 351C, 750 VAC, C10, 9" LSD
Air, steer, power windows................