One of the most common calipers used in the aftermarket today in many companies disc brake conversion kits are the exact same General Motors based calipers we use in ours. It is a very good caliper that will work for many different applications.
There is a drawback though. Many people in the classic car/hot rod don’t use the emergency brake. I can say this from previous guilt on this subject. In fact, some people don’t even have the emergency brake hooked up. You might ask “If you don’t need it and therefore don’t use it, why is that a drawback or a problem?”
When the pads wear and material is removed, the pads then become further away from the rotor surface. The calipers use a “one-way clutch” or “sprag” inside the caliper piston. When the parking brake is applied, the sprag will recognize when there is 0.030” or more clearance between the friction material and the surface contact area on the brake pad. When the distance is 0.030”, the sprag turns inside the piston adjusting it outward and keeping the rear brakes properly adjusted.