[FirstOwner69]

Since this appears to be on the verge of becoming a comprehensive DG4 mirror thread, I figured I'd add some observations I've made over the last 50 years or so.

I've found that there were 2 DG4 bracket variations between 1969 and 1971 in addition to the 1972 style.

Regarding the 1969-1971 styles:
This information is based on my 1969 originals and a set now on my 69 that I got from a 1970 GMC. The most common, by far, appear to be the type I got from the 1970 GMC. Both utilize the same hole pattern in the doors.

Vertical Supports/Legs...
The first version vertical supports were like the originals on my early 69 (picture 1). They were quite straight at the bottom whereas the second version bowed out from the door (picture 2). My assumption is that the bow may have been added to provide additional clearance with the upper beltline molding as a result of shortening the horizontal door support. Was that molding not available until later in 1969?

Horizontal support to door...
My first version horizontal supports (picture 3) measure 6-7/8 ". The second version (picture 4) measure 5-1/4".

Mirror heads...
The mounting brackets on my original mirror heads were offset vertically which allowed the owner to raise or lower the head by flipping the mirror. Most others I've seen are centered. I have no idea when that change occurred or if mine are truly unique. In an earlier thread I read, someone claimed that this was a Ford design head, but I'm 100% sure mine are original to the truck. Picture 5 was taken the week after I bought the truck in 1969 and clearly shows the offset.