Can't say for sure about a dart but I would imagine it would be the same as my barracuda. Of course you had paint that was body colored in the engine bay and slightly into the tranny tunnel. This paint could also be on the frame rails in this area. The inside of the wheel wells was also painted body color. The actual bottom of the car was not painted. This was true from rocker to rocker and from trunk extension to trunk extension. There was some evidence to suggest that the metal had a zinc coating at one time. In other words, the car got painted where the paint guys could hit it, but there was no effort to actually paint the underside of the car. I also had undercoating inside the wheelwells and up on the frame rails inside the wheelwells. My car was not undercoated on the whole underside. My personal plan is part way done. I used a needle scaler to descale the underside and take off all the undercoating. The undercoating was that old black stuff that had hardened up. I have also seen(on my 69 Bee) some snot colored stuff that is still gooey. I will then media blast the underside(on a roto), expoxy primer the underside and hit it with single stage paint that will be body-colored. It looks nice, provides some rust protection, and if you mess up the underside, so what. I will also do this inside the engine bay. I have often heard that if you only have 2-3 runs in the engine bay, you did a better job than the factory. Hope this helps.
