Know how to read GM instructions for bolt placement?

[71CHEVYSHORTBED402]

I honestly don't know how and that bugs me. I'd really like to know how. I'm no engineer, which goes w/o saying at this point. Never even assembled a model....ha!

First, are the measurements in inches or metric? If inches, 2.28 say what? (Slightly less than 2 9/32").

Second, where's the reference point? There may be one, but I'm not seeing it.

Third, I'd expect to see a measurement from the edge of the door. I don't see that either.


The first picture are the instructions.

The second is of a nice illustration for the passenger side. He says the penciled line is 1" below the door body line. That's confusing as well, as I'd expect that line to center between the two holes, though I don't have the hardware in front of me. I'm assuming mirror placement is square. It's my understanding the mirror on the driver's side would be 1.3" further forward.

The third is a nice illustration of the passenger side on.