1967, 1968, 1969 Pontiac Firebirds were built off the Camaro body, but were basically the "rich man's Camaro".
Plymouth Roadrunner was a different body than the charger but produced the same performance results. And Plymouth SuperBee/Bird were basically the charger with a few differences like engine size, color, and accessories options.
The mustang was a much differently styled car than the Camaro, but was always in competition with it.
Much more to say, but that should give you an idea.