Rear brakes of just about all GM rear ends are interchangeable. Bigger cars had bigger drums with wider shoes, and larger wheel cylinders as well, but you can bolt them onto all of the available rear axles (that is the 8.2" 10 bolt interchanges with the 8.5" 10 bolt which also swaps with the 12 bolt backing plates). However the hydraulics must be matched (if you change a wheel cylinder size drastically you must make a suitable change to the master cylinder as well). Front brakes must match the spindle (steering knuckle) you use so often that is changed as well to upgrade the brakes (and also lower the car).
Companies like SSBC have done all of the parts matching for you and will sell you a GM compatible brake system that uses stock parts obtainable at the local parts store when they eventually wear. Many custom brake companies with exotic parts require you to go to them for replacement parts.