And then there is my, "something's fishy" about that Dart.
fstbackfish ,my car I started with was a twin to yours. Red 68 and as bad.Mine had been lightly rear-ended. Needing every panel done is what allowed me get creative. Note the red roof.
Does the import have separate bulbs for signal and stop? Does the trailer have one bulb for both? If so the systems are different and you buy an adapter to make them compatible.
another major change up was the 01.5 disc brake dana 80 rear end. earlier models with drum brakes are dana 80h. h is for hybrid, as in the axle tubes downsize and use dana 70 outer bearings and drum brakes. full dana 80 with a disc brake truck.