".... if the glove fits ..." LOL

That link on the frames is not quite accurate...

64-67 did all have the same 115" wheelbase, but the wagon and El Camino were 3-1/8" longer in the rear than the coupe/convertible/sedan frames. Convertible and El Camino were boxed, all others were open C channel rails. (except '65 Z-16 396 coupes, those were also boxed)

68-72 2-door car models had 112" wheelbase. 4-doors, wagons, and El Caminos had the 116" frame. 4-door (116") frames were the same as the coupe/convert behind the axle. Wagon/El Camino (116") frames were 6-1/4" longer in the rear than the other models, and they have the upward curve at the very rear of the frame, so the rearmost body mounts are 1" lower than the other models too. Again, El Camino and Convertible were the only models to be boxed.

I have scans at home of the Chevelle pages of the '66 and '69 frame dimension charts used by body shops for frame straightening... can post later if you need them. :)