Canadian cars?

No, the last year a US A-body was substantially different from a Canadian A-body was 1966. Canadian-built '73 Darts are the same as US-built '73 Darts, front to back and top to bottom, with only very minor details differing; for example a Canadian-built car will often have a Transport Canada decal that looks like this in the driver doorframe area not far from the US Vehicle Safety Certification Label.

Quad taillights aren't indicative; those were on all '71-'73 square-body Darts, though there is a minor difference between the '71 lenses with metal inner deco rings and '72-'73 lenses with cheaper silver paint instead.

The '73 car probably did not come with "1972 brakes" (what is it you have in mind when you say this?). Yes, you can directly swap on '67-'72 doors with vent windows if you want them, though you'll lose the side impact guard beams built into '73-up doors.