The early cars came with 6-piston Wilwood Superlite calipers on all 4 wheels. Front rotor diameter was 13" and the rears were 12". These were and are great brakes, but were designed for a smaller rotor package than became popular over the years, and lacked dust seals so were higher maintenance on the street, as well as not being legal for the street in places like Australia. Eventually they were replaced by the current Brembo package.
The Wilwood brakes are based onthe billet "Superlite 6" calipers. These calipers use the conventional 3.5" center lug mounts that are common in the Wilwood line. The maximum rotor diameter they are designed for is 13.06". Rotors as wide as 1.25" are supported, and thinner ones can be accommodated with thicker pads. A complete technical spec can be seen here: WilwoodCalipers.pdf
There is a different part number for each corner, so when installing them, don't get them mixed up. To validate proper installation, the calipers must be installed with the pressure inlet toward the center of the car (in order to attach the brake line correctly- otherwise it would interfere with the wheel. In addition, the bleeder screw must be facing UP, not down.
The rotors are standard Corvette C5 fare, and can be obtained from all Corvette specialists or auto parts stores. To be sure you have the correct rotors, measure the original ones and the new ones before you install the new rotors.
There are plenty of options in terms of drilled and slotted rotors. And substantial weight savings can bo obtained from 2-piece rotors. For example, 2-piece rotors for the Wilwood brakes can shave 10 lbs each off the front, and about a pound in the rear.
The Wilwood calipers have a wide range of pads in many different compounds, available from Wilwood and many other sources. The BP-10 pad from Wilwood is usually recommended for the street, with track and race pads available from many sources in addition to Wilwood.