Apparently, to hide the ugly flange of the rocker panel pinch weld lips, Ford painted that lip with black paint, with the exception of dark cars. However, if the guy on the line zoned out while working, even a black car could have black paint sprayed on the pinch weld joint. Here are some pictures of my car showing the pinch weld black paint...
The picture above is the rocker panel area forward of the passenger side door. The picture below is the rocker panel between the rear of the passenger door and the rear wheel well.
The next picture is the driver's side rocker panel between the door and the rear fender well. You can see the front leaf spring mounting perch.
The next shot is the rocker panel at the rear edge of the driver's side door.
The one interesting note of this paint is the way it's applied. It obviously wasn't sprayed by a typical spray gun. I'll have to do some more reading on this. It's not like I have to have this sorted out now. But at least I have the pictures to document it. I'm probably going to go with tinted epoxy primer for the red oxide and match the interior tint which looks to have a brownish cast to it.
If I can find some time this weekend between preparing to move my mother-in-law to a rehab facility and other commitments, I may get to actually cleaning up the bottom of the car. I'll use the "whirly bird" wire brush on my angle grinder to knock off the surface crud. Then I'll determine the next step in getting down to good metal. I also have some photos to take of gas, brake, and exhaust mounts for more documentation. I'll swing by Thrifty Supply to get a new and bigger Argon/CO2 tank. Then I can start working on finishing out the underside of the floor pans. All in a days work, right? LOL!