Yeah, according to your book the technical term for post is "thin pillar" that is more commonly known as a "post" car. Probably because post is faster and easier to say than "thin pillar" is?
From my dad's old "Brief Passenger Data" books (Ethyl Corp, 1964) the 64's are lightest of the lot, unless you go Chevy or Mopar. 1964 Special v6 2997 v8-2995 1964 Malibu I6 2870 v8 2995 1964 Dart v8 2630 1964 olds v6 2953 v8 3127 1964 Pontiac I6 2974 v8 3230 1965 Special v8 3143 1965 Pontiac V8 3219 1966 Specialv8 3307 1967 Special v8 3354 1968 GS 350 3497