Fourth generation (1965–1970)
For 1965, All GM “B” body cars were dramatically restyled. Swooping rooflines, rakish fender lines and the “Coke bottle” profile contributed to making one of the most popular body styles ever produced. The Bonneville got the new styling, with plenty of bright trim on the lower body sides and on the rear deck. Inside, new upholstery and instrumentation were featured. Drivetrains were essentially the same as 1964, except the Turbo Hydra-Matic transmission quadrant, which now featured “reverse” in between “park” and “neutral”, instead of at the bottom of the selections (below “L”), the old arrangement having been sharply criticized as a safety hazard.
A General Motors corporate edict that took effect with the 1967 model year led Pontiac to discontinue the Tri-Power engine options on all of its cars. That year also brought a larger 400 cu in (6.6 L) V8 as the standard engine for Bonnevilles and other full-sized Pontiacs to replace the previous 389, while the 421 cu in (6.9 L) V8 was replaced by a new 428 cu in (7.0 L) engine that offered as much as 390 horsepower (290 kW). Also beginning in 1967, carburetion was changed. The previous standard 600 cfm Carter square bore four-barrel and optional Tri-Power was replaced with the new Quadarajet spread bore carburetor delivering 800 cfm, equivalent to the previous 1966 Tri-Power set-up. For 1969, a 360 hp (270 kW) 428 became the standard Bonneville engine, which in turn was replaced for 1970 by an even larger 455 cu in (7.5 L) V8 rated at 370 hp (280 kW).
The 1965-70 GM B platform was the fourth best selling automobile platform in history after the Volkswagen Beetle, Ford Model T, and the Lada Riva.