Sometime during 68-70 the mirrors moved back a couple inches so that instead of looking through the vent wing, as in 66/67, you were looking through the door glass.
IMO a minor improvement in visibility, but a much worse head turn for line of sight to the mirrors.
If your driver's mirror doesn't get hit by the wing...and you match that for the pass side...then the pass side shouldn't get hit.
...and to clarify what I said earlier- I've never heard of mounting locations being different left to right anywhere else.
...and...and I'll tell you what...NOT having a pass side mirror in todays idiot circus traffic SUCKS.