Unfortunately, it's very hard to identify the exact camera position, since alignment of foreground objects can be matched from different positions at the expense of matching the original perspective. Old cameras had huge imaging plates, with low crop factors, I suspect what happens with a lot of these old/new match-ups is that the photographer is standing far from the original spot to achieve "best possible" alignment with the foreground crop - which of course screws up your perspective. You could align against the background, but then you'll have poor alignment on the foreground.

Cleaning up the crop/zoom in photoshop does not help you unless you are shooting from the exact same spot to get the same perspective.

http://www.digitalcameraworld.com/2014/08/15/debunking-the-m...