Those are very interesting wheels if you're a steel wheel fanatic (which I am). They appear to have the early style center with 3 hub cap bumps, a somewhat curved surface, and the slots between the center and the rim are curved and parallel to the rim. The center of a disc brake wheel is flatter, and the slots between the center and the rim are almost straight across forming more of triangle shaped gap. However your centers appear to be mated to later model rims with safety beads (indicated in the photo) at least on the back side.
I can’t tell if they have safety beads on the front from the photos. Most of the early wheels I have seen don’t have safety beads at all. Although Chrysler invented and produced the safety bead rim since 1941, I don’t believe GM used them until the mid-late 60’s. So - your wheels are no doubt the original drum brake wheels, but apparently engineering changes were occuring that modernized the rim portion at least.
In any event, I’m thinking those will fit over stock disc brake calipers, both because of the cylinder shape of the back of the rim, and also because the backspacing is so shallow because the rim is so narrow. The part of a drum brake wheel that normally interferes isn’t there. I would certainly fit them up before spending money on other wheels.