I did a stereo install in the mid-70's on what I remember being a Dodge colt. When I was plugging in the antenna cable, I noticed it didn't have one on the car & there were no wires in the windshield, either. Finally traced the antenna wire & it was hooked to the trunk lid, which was isolated from the rest of the car by rubber/nylon bushings, including the latch. It worked great but I can't remember if it was factory or not. I did the same thing on a couple of other cars I built, shielded wire to trunk lid, shield wire to body, with good results.