Will these 17" wheels work on our Dart?

You’re on the right track with the front backspace. With BBP, 73+ disks the max backspace you can run is about 5.6”. That’s because of outer tie rod interference. It does depend on the design of the rim, but 5.6” is s fairly safe bet.

With a 7” rim you don’t really need to worry about having the max though, because the widest tire you’re going to put on a 17x7 is a 235/50/17. And that means you could run a 17x7 up front with a 4.5” backspace. You can’t even run 245/45/17’s with a 7” rim, so you don’t necessarily need to max out the backspace. You could run any backspace from 4.5” to 5.6” with a 17x7.

Now, step up to a 17x8 and a 255/45/17 and you need 5.25 to 5.6” for backspace.