Chevy was the entry level car but GM made other marquees where the difference in price was reflected in the number of creature comforts that where added as options to the interior. As you moved up the price bracket ladder of the various marques more and more parts formerly offered as options where being bundled together as standard equipment. So what is a very rare option on a Chevy such as a tilt wheel is considered standard equipment on a Cadillac or a Buick. All of these parts interchange across the B-body platform for the same series (years) of cars from the interior to suspension parts.
Before 1972 only the motors where truly unique to the name plate (though Chevy had it's own unique transmission bolt pattern and all of the other GM cars shared a common bolt pattern called BOP). After 1972 GM put Chevy engines in all of the marques if you ordered a V-8, and a Buick V-6 if you ordered a V-6 (straight six was also a Chevy engine). In the early eighties GM developed a new line of V-6 motors to meet different applications with the V-8 being intentionally phased out of production to improve CAFE numbers as best they could; though the public refused to cooperate.
For every model Chevrolet sedan made there is a mate made under another GM marque. So for your Chevrolet Biscayne, Impala, or Caprice there is a Pontiac Bonneville, a Catalina, or a Parisienne, from the Oldsmobile division there is the 88, or the 98, from Buick you can find a LeSabre, or an Electra, finally from Cadillac there is the DeVille. The Cadillac Fleetwood, and Brougham are also Impalas from the fire wall forward, but the body has been stretched with an extra ten inches of car placed in the rear seat area starting with the rear seat foot well. These Cadillac cars are known as a C-body or D-body to compliment all of the other cars I named above being a B-model car (rear wheel drive, full size car).