Also, with Buick dropping its 455 V8 after 1976, continuing the '77–78 Riviera on the old E-body platform would have forced Buick to either downsize its engine compartment to their 350 V8, which was too small and underpowered for a 5,000-pound car—or "import" larger engines from other GM divisions including 400s from Chevrolet and Pontiac, Oldsmobile's 403 or Cadillac's 425—each of which would have limited sales and production as each division gave first priority to its own vehicles before selling engines to other divisions.