In the mid-1960s, Buick engineers had a lot of leeway in their engineering compared to the other GM divisions, and they were able to spend more money on their cars than any division save Cadillac. It certainly showed.

One big difference was the superb, lightweight 300-cid V-8, stroked to 340 cubic inches for 1966 then bored out to 350 for 1968. The engine weighed but 467 pounds — about the weight of the Chevrolet inline sixes of the day — yet was top quality, precision-cast and manufactured at Buick’s own Flint, Michigan engine facilities. The distributor was in the front, facilitating easy maintenance of points and condenser, and spark plugs were easily reached. While the weight went up slightly when the engine displacement increased, the ease of maintenance and quality did not change.

Likewise, the chassis showed advances shared by no other cars. Buick had developed phenomenal bi-metal (alloy-finned, iron-lined) drum brakes for 1958, and these were only improved as time went on. The 1965–67 Super Turbine 400 automatic transmissions also featured a reliable switch-pitch torque converter. The optional “nailhead” 401 V-8 of 1965 on the LeSabre was powerful and reliable, making for a fast ride, with phenomenal brakes and handling. Overall, the LeSabre was a terrific middle-class family car, as was intended by Buick.

While the ride was always excellent on these cars, when equipped with bias-belted or wide-oval tires, handling became far better than anyone could reasonably expect — while leaving the cloud-like ride alone.

The buying public caught on in the mid-1950s that Buick quality and value were excellent, contributing to Buick moving to 3rd in the sales race, but by 1965 GM’s Pontiac Division had moved into that place with their emphasis on youth and performance. Of course, Buick offered high performance too, but at a higher cost.

Both body and frame were both all-new in 1965, and the Buick LeSabre lineup included the choice of convertible, two-door fastback hardtop, four-door sedan, and four-door pillarless hardtop. These remained through 1970. Base and Custom trims were available, with the convertible limited to the Custom line. The wheelbase was 123 inches, giving plenty of room for up to six people and their luggage.

The 1966 cars saw the aforementioned 340 V-8 take the place of the 300, with increased torque available for the driver. This sharpened up the acceleration both in town and on the expressway. The base engine utilized regular gas and had 220 hp. The 401 was removed from the LeSabre option list, replaced by a new optional high-compression four-barrel carburetor 340 V-8 producing 260 hp. The cars featured a new grille, taillights and trim.

The 1967 cars saw a body reskin with a new sweeping contour line. Naturally, new grille, taillights, bumpers and trim were included, as was a revised interior. Another new option was the massive opposed-piston Bendix ventilated front disc braking system, shared with no other GM division but Cadillac.

In 1968, the LeSabre saw the introduction of the bored-out and improved 350 V-8 of Buick’s own design, though it shared the same displacement as other GM V-8s. Power moved up to 230 and 280 hp. The car was lightly facelifted, with a new split grille.

The 1969 cars saw another exterior body refresh, including more formal rooflines, with the two-door fastback eliminated. A massive split grille within a combination bumper and grille surround was a noticeable change up front.

Model year 1970 was the final car of this generation, and it was only mildly facelifted, with one notable exception. For the first time since 1964, a full-sized Buick station wagon was offered, the LeSabre-based Estate Wagon. The engineering staff decreed that Buick’s new big-block 455 V-8 would be standard equipment on this car, and also relented to public demand and allowed the same massive 370-horsepower engine to become an option on the LeSabre — the first big-block LeSabre since 1965.