The reason why I'm asking is that 1977-91 Impala/Caprice wagons had shorter doors - an inch or two at least. The wagon looks longer. Does it have the same wheelbase?

Seems longer? Or is that just an optical illusion?

http://www.chevelles.com/showroom/FO_FDYFO/Mvc_011s.jpg

are you asking about 68-72 doors?
this is a complicated question you are asking. be more specific. there are 4 door hardtops and 4 door sedans. 70-72 4 doors are completely different from 68 & 69 and wagon but 68-69 sedan 4 door rear doors will fit on 68-72 wagon, not the hardtop.

Be more specific. there are 4 door hardtops and 4 door sedans.
70-72 4 doors are completely different from 68 & 69 and wagon
but 68-69 sedan 4 door rear doors will fit on 68-72 wagon, not the hardtop. 68-72 Sedan I guess. The lines on a sedan don't match up to a wagon though, do they? The wagon has an elky-style curvature?
I should take my question back.
But now that you mention it, you are saying a 68-69 4-door sedan rear door won't fit on a 70-72 sedan in that case?
The 68-69 has the same curvature as the wagon, and the elky in that case?

But now that you mention it, you are saying a 68-69 4-door sedan rear door won't fit on a 70-72 sedan in that case?
right
The 68-69 has the same curvature as the wagon, and the elky in that case?
right