To continue on the subject of adding a passenger side mirror, I'd like to offer some info gathered on the subject.
Several months ago I was on the hunt for a driver's side door. I found one in southern NJ, still intact, installed on a '71 280 SL parts car. While looking for other usable components I noticed two side view mirrors on the gentleman's bench. As it turned out the second mirror was a US passenger side mirror which was installed at the factory on this particular car. Long story short, I purchased two doors and two side view mirrors.
Below are pics showing the reinforcement / backing plate as installed at the factory. One weld is visible. There may be other(s) hidden behind a spot welded lip at the top of the door. I'll attempt to look closer.
As mentioned in another thread, I believe a similar plate can be fabricated and bonded with auto panel adhesive. To me this is the least invasive and most effective approach. If not familiar with these two part adhesives, believe me, they are in many ways superior to traditional welding. However, the visible weld does add rigidity as the plate is secured on (pretty much) a right angle to a structural piece of the door.
Also, it appears that the door skin and backing plate were tapped together to accept the mounting bolt. Were nuts used as well?
I will attempt to provide backing plate gauge (thickness) in the near future.
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On the other side of the panel I measured and noted dimensions for proper placement of mounting holes. Instead of sticking with one measurement standard I used both US (inch) and metric (mm). With this approach I was able to get dimensions as accurate and even as possible with relatively generic rulers.
Since the area is contoured I used a piece of paper to conform to the curves and mark precisely. I then took the measurements off the paper. Using this technique in reverse may make life easier for anyone taking on an installation.
I used the very tip of the chrome window molding as a starting point. My assumption is that it's harder to accurately describe a starting point on the curved edge of the door. Especially if the edge was modified while fitting up to a fender during repair or restoration.
I will amend this post as additions, deletions, corrections and other edits become necessary.
Feel free to ask questions while I have these parts available.
