[Stocker]

Someone correct me if I'm wrong -- DG4 mirrors were available on '67-'71 trucks with the upper arm shown in Jeff's pics (post #8). 1972 trucks also had DG4s but the upper arm was different, and lower mounting points *may* have been different than on '67-'71s.

Here's a pic of a '72 DG4 for comparison to Jeff's mirrors. The lowers are shorter also. Plenty more pics on the site if you do a search.