Motor mount brackets and the dozens of other black brackets on lots of Mopars were typically dip painted in black, oil based enamel. Look closely, and you can find the paint runs. Large water vats were used that had a film of the black enamel on the surface of the water, and the parts were dipped in this. This method was easy and quick and prevented any overspray and waste, compared to spraying paint. The biggest parts on my car that were black enamel dip painted were the frames and springs of the bucket seats and rear bench seat.
See photos and discussion here:
link Another method of painting brackets that must have been very messy and inefficient was literally pouring black paint from a paint spigot onto the brackets. This method made for very thick paint coatings and might have been at Lynch Road, and I believe this method is discussed somewhere on this large site
here.
Around 3 dozen or more black pieces of steel on my car were dip painted with enamel and have noticeable runs. Some examples are brackets of motor mounts, parking lights, steering column, license plate, parking brake ratchet, etc. Big black pieces on my car, the K frame, steel wheels, and the rear axle housing were spray painted black, not dip painted.