Remote Mirror ??
 

These 2 remote mirror bases look exactly the same to me, size, hole, etc yet have 2 different part numbers. One has number 9780049, the other 9787847. Do we know why?

I can't find a listing for the part numbers. Could one be for the left side of the car and the other for the right side?

No, they are both LH.

GM part numbers are as followed - LH is odd#s. and RH is even#s.

More than likely, 1st and 2nd design.

Buick also used the same mirror only with a different cable length and control knob, therefore different part number.

As far as all lefts are odd numbers and all rights are even...... That isn't always the case.

They look the same, because they're based on the exact same mold.
They might've beefed up the casting in someplace inconspicuous?
I've taken the liberty of rotating one of yours, added one of mine.

http://forums.maxperformanceinc.com/...1&d=1578497916

Since its the same basic mirror for 65-68 on A,B and F bodies, I believe it's the angle of the mirror head to suit the different bodies that determines the different part numbers.
For example my 68 GTO remote base has the 9787847 part number.

These have the same angle for the mirror head, measured them. There are 3 different mirror bases I am aware of, the angle and the way they attach to the head are the differences I see and I think one uses a different mounting screw.

Different mounts and mounting screws are part of 1st and 2nd designs. I think it was '64 or '65 where there were 3 different designs. These design changes, for the most part, were minor but still carried a different part number. I don't know if these design changes were something GM came up with or if it was a supplier thing.

I have this one LH base that blows up the LH is odd#s. and RH is even#s theory. It's obviously LH with even number, head angle is also greater then the originals 1st shown. This shows 9787848.

While we're on the subject of mirrors, are the passenger side units hard to come by? I see that Ames has the drivers side only, noting that it's ornamental only when mounted on the PS.

That picture brings back memories, I worked with a guy that could not stamp a part number in a mold straight to save his sole. lol... Half the time the numbers were upside down or back wards.

I see number (1) and (3) in the design, it could be possible that the mold had multiple cavity's creating the same part. Also these cavity's were all a little different creating parts fitting a little better than others.

I have both mirrors and while they have minor differences the shape is exactly the same. The internal parts are slightly different. Possibly 2 different manufacturers.