Here are three examples of brake distribution blocks. The four-wheel drum-brake distribution block for 1967-'69 is "A." Front-disc brake applications for 1968-'69 received "B," with a built-in proportioning valve. For 1967, the proportioning valve was located above the rear axle. The Master Power Brakes' version is "C," which works well for custom applications, where originality doesn't matter.