I think what he's saying is the new tool '61 and '62 are Catalinas and /or Venturas which were built on a shorter chassis than the Bonnevilles.
The Chevys did not share thier chassis with the American full size Pontiacs. The Canadian full sized ones [Parisienne] did but that's as they say, another story.
and the Trumpeter Bonneville also used a different chassis.
Also the kind of "shared components" swapping you mention didn't really start with the full size cars until the '71 on cars. Before that, in the 60s and '50s they only shared small stuff and each mark had thier own unique engines and chassis.
So, yea, there are no direct swap chassis for the full size '60s Bonnevilles.