Carl,
I have ran into two problems with switching out mirrors from a different coach. First was that even though the mirror base fit against the coach body, there was a slight difference in the taper that was made into the mirror base so that the mirror arm did not set parallel to the ground causing a very restricted usable viewing field. The other problem was that the color code and wiring plug did not match, so it was difficult to wire into the new coach system.
Gerald