Most of the cars had gray primer some early cars did have red oxide. Under the front fenders Ford applied seam sealer to like the torque box and where the rocker meet the A-Post and down between firewall and inner. Then they applied 3 coats of epoxy primer. You can find this info in the Ford Fact book. Then they applied the black to the under hood area and if you had Decor Group. Then they applied color. The front fenders were not on the car. I have seen original cars with lots of body color on the outside of the inner fenders and some with just a little. The rear wheel house got seam sealer and a half ass shot of undercoat, same inside the trunk. Then primer and color coats. The floors along the rockers and the wheel house got color over spray. So you might see some primer and also some color. They DID NOT go back and paint black. In the trunk it was assembled with tail lights wiring, fold down, side marker lights and then they sprayed the spatter paint. It got on side marker lights wires, gas fill pipe and some on tail light housings. Most people over restore a car.