My Hamtrack '72 'cuda was dipped in a dark gray primer. You can see the dip line on the rear fenderwells. Resto Rick sells a primer that duplicates the correct color. The body color was shot with doors, hood, and decklid bolted on (without latches installed). Color was applied from floor level, thus there is a little overspray on the bottom and a little into the car. I suppose if they were at the end of a run of that color or at the end of the shift, they might have sprayed what color they had left to get rid of it, as in spraying more color into the interior. The blackout paint was sprayed with the radiator and fenders installed by a guy in a pit as the car rolled overhead. This is why you will see color on the top-side of the radiator yoke and black on the underside and flat portions. Overspray of black onto other surfaces was common.
I believe that all cars had undercoating in the front and rear wheel wells. This was to keep the paint from chipping. It also helps keep noise down. Also note that undercoating was applied on the inside of the quarters and doors for sound insulation.
As for POR-15 on the bottom side, has anyone run into adhesion problems? I keep hearing that POR-15 really likes surface rust as a substrate. Some guys have reported that POR-15 won't adhere to a non-rusty surface.
I'm considering undercoating the entire underside of the car, but I'm worried about 2 things. First, when I go to sell the car, I'm worried that potential buyers would be scared off by the undercoating as many guys use that stuff to hide problems. I suppose lots of before and after pics would help on that issue, but buyers are always advised to beware of undercoated cars. Second, I'd hate to have to remove that stuff during a second restoration or for repair work! Any thoughts on the bad vs. the good?