Originally Posted by Z28SSMAN
Some articles say all 58-64 GM's used the x frame, it appears that '59-'60 Oldsmobile took quite a bit different route. They were also the only ones using rear leaf springs. The Super 88 & '98 Olds also had a different wheelbase than the Dynamic 88.
Oldsmobile never went with the Tubular-Center X design without side rails. Their design was pretty traditional since 1933 but did alter the X bracing for 1959 and 1960 which made the frame a combination of both chassis designs. It was quietly dropped completely in 1961 for a perimeter frame with torque boxes.