Just an fyi: (sorry if this is killing the GTO thread)
There were 3 different frame types: The Chevy (or Detriot) frame like this car has, which is extruded tubing. It has a recess squeezed into the top and bottom for strength. It was bent to shape and left wrinkles in the inside radii like bending a tailpipe. There was an A.O. Smith frame which was a welded opposing channel frame with extra reinforcements for convertibles, and the Budd frames which were the standard welded channel frames. Except for the convertible frames which were used only on those models, the other two types were used at random on all models as they happened to come in to the assembly plants. In '64, a reinforcement was added at the assembly plant to the rear control arm bracket on 409 cars.
