Post a picture of the build sheet if you can find it and also the fender tag. This will clear up any questions on the cars value. I think the 340 canadian cars were called western special or something like that. Very few made so they can be valuable, or at least more so than a regular dart.
Looks like a nice color combo for a 73. Most were ugly creme or green. Also looks like a black interior, score. The steering wheel looks to be pre-73 though. Maybe its an early build 73.
Great price on that car. That is 10-15 year ago pricing.
Judging by the lack of rust and the way the paint is baked, it probably lived most of its life out west. Is the interior baked?