In fact, a 1966 Chevy comes in relatively svelte at well under 4000lb well-optioned, compared to the mid-size SUVs and minivans that are popular today. 226" is about the length of a stretched Buick, i.e. "Electra 225". I guess the 66 Chevy is at least a foot shorter than that.
Sixties and seventies Chryslers and stretched GMs had the longest trunk interiors. FoMoCo exchanged length for depth.