The last great dinosaur made by Detroit, a body on frame vehicle which was the last of its kind, the B frame 1991-1996 Buick Roadmaster whose frame was initially designed in 1977 which was also shared with the Chevrolet Caprice/Impala, Oldsmobile 98/88, Cadillac Fleetwood and Pontiac Bonneville. When these vehicles were sold, the auto industry was going to the unibody construction which made vehicles lighter and more fuel efficient. The body on frame construction is much more flexible which allows for vehicles to be modified. Why do you think low riders are all body on frame construction? Or Hot Rods? And that's why pickup trucks are body on frame. They are naturally much stronger than unibody.