Also, the police wheels are LBP, so I don't believe that the rear is from an A body, but more likely a transplant from an early B body, which may explain the 742 center!
Or just aftermarket or re-drilled axles. Even the 65-67 B rear probably wouldn't work with the stock backspacing on a set of police rims, that rear is still over an 1" wider per side than an A body 8 3/4. Even the police rims with an A-body 8 3/4 that's been converted to BBP limit the tire size to a 225 on a Dart.
The "super six" was a "D" code engine. Of course it didn't start until 1977, but neither did the super six.
As far as the mirrors, they aren't listed as part of the trailer towing package in the literature. Of course that doesn't mean it didn't happen. The options that came with the trailer towing package in '73 are in the link I posted above.
