I went through the same thing with the mirrors, must have been 83' they changed to the chunky square type. My 81' wagon had the slimmer skinnier type until a careless bump from a wheely bin shattered the stem of one and sent it to the concrete. I don't remember having to drill the large center hole though

Nutserts are a good thing, usually

If the screw gets cross-threaded and in the insert spins, it's a world of pain. Also worth doing if you haven't already, paint the bare metal edge before the nutsert goes in the hole. Even slather wet paint on it and crimp the nutsert into the wet paint, none of mine have rusted around the edge...yet...