Antennae Repair? 1968 Dart

found this and a lot of info comes back to a screw in mast. I do not think from the photos you have posted that the cable is supposed to be removable.

But the more I look the more I think the 67 vs 68 up antennas are very different. 67 mast is not removable that I can see.

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Assuming for a moment that the cable is supposed to be removable. there is a possibility that the screw in part of the original mast is broken off inside the housing and maybe a drill and easy out could remove it. don't drill too deep! so you might be able to repair it. BUT if the cable is not supposed to be removable then it is moot, just get a replacement or used one.