I guess I need to ask: what are you trying to accomplish? Stock drum brakes, properly maintained with quality parts as needed, are entirely sufficient for street driving on street tires, and is the least expensive way to go. For a street car, if you can lock the wheels at speed (and stock drum brakes can do that), that's about all any brake can do for you.
AFAIK, an upgrade is only needed when you intend to drive much more agressively (Gymkhana, slolam, road racing, etc) at high speeds on sticky tires and you're concerned about brake fade caused by frequent/sustained braking and the attendant high brake temps that can glaze shoes & drums.
Yes, disk brakes stop somewhat better and run cooler, so they can handle a greater number of rapid stops in succession without fading. It is not super expensive to simply replace your system with a (used/refurbished) stock Corvette disk brake setup.