Easy8 posted the above picture. Hoping perhaps if this is HIS Fiero, he will chime in on what they are from and how he was able to mount them.
Examining the picture a bit closer, it looks like perhaps there has been a gusset added to the corner of the door to allow the mirror to be mounted as the face of the mirror base appears to be flush with the face of the door skin. The mirror also kinda looks like the mirrors on my wife's Malibu.... I'll have to look at them tonight when I get home.