Dart GT side mirrors

MmmmÂ…not that I've seen. The housing head is very slightly different in design detail, unique to the '64 and then differently unique to the '65, but from what I've seen over the years '66-'76 A-body and '66-'70 B-body remote mirrors are all the same as far as the housing and glass go. The only differences are short (4dr + 2dr w/vent wing windows) vs. long (2dr w/o vent wing windows) cables running from the control to the mirror, and minor differences in the shape of the control knob.
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Here's a photo of three different remote mirrors. The one on the left is a '66 model, the center is a '67, and the right is a '70. As you can see, the control is much bigger on the LH one. Other differences on the LH one is the base is not attached to the head. It is just sandwiched between the head and the door shell. Also the round part of the head is tapered more steeply toward the glass. The later ones are almost straight.