On the topic of the cage/roll bar…when I bought my 69 Dart it came from out of province, so I required an OOP insurance inspection. It had a 6pt bar, frame connectors, Cal Tracs, 451 stroker, etc. No mechanic shop would certify it. It is, as Speedy said, due to the change in crash characteristics. Had to find a shady fella to certify it as per the specs on the vin. All mods were done after the inspection…..if anyone asked.
At the end of the day, it was a street legal race car. But due to the often mentioned reasons in this thread, mileage, noise, heat, uncomfortable, etc….I sold it and bought the Hellcat, which is faster, and a street car.