During the cleaning of the rear axle and 8-3/4 out of my 72 Challenger Rallye I made a discovery on the center section that I've never seen before (or maybe I have not been paying attention in over 25 years of wrenching on e-bodies)

This is a low mileage original car that I purchased from the original owner over 10 years ago while living out in cally so the underside is in excellent condition.

Check out photos of the 8 - 3/4 center section.

At first I thought it was rust but the more grease & dirt removed it became evident that the center is painted with red oxide primer. All the original paint markings and codes are on the axle tube, center section etc.
My experience has been that the center sections were finished (or left) natural steel.