In 1958, the Bonneville lineup expanded, offering a hardtop coupe and a convertible model. Both cars were built on the 122-inch Chieftain wheelbase and featured distinctive trim and appointments. Equipped with the potent Star Chief’s 255 bhp V8 engine, the Bonnevilles stood as the most luxurious and expensive offerings among Pontiac’s lineup. An optional “Tri-Power” setup with three Rochester two-barrel carburetors became available, offering higher performance at a lower cost than the fuel injection option, which resulted in limited orders for the latter.
In the following year, 1959, General Motors redesigned all of their cars, and Pontiac stood out with its exclusive “Wide Track” chassis. The Bonneville series was now referred to as “Bonneville Custom” and introduced a new four-door Vista hardtop and a 389 cubic inch engine with a four-barrel carburetor. The Hydra-Matic-equipped Bonnevilles had a compression ratio of 10.0 to 1, leading to an output of 300 bhp with the four-barrel carburetion. Furthermore, the Bonnevilles were now based on the 124-inch Star Chief wheelbase.
In 1960, the Bonneville lineup saw the addition of a well-equipped four-door station wagon, but this particular model received limited orders. On the other hand, the convertible variant, with a production of 17,062 units, proved to be popular among customers, although it was still less common compared to the 39,000 Vista hardtops produced in the series.