Yes, they should fit, although 4.5" is about the least amount of backspacing you can get away with. I'd run more, even with 17's you should have enough clearance on the tie rod end to run more backspace, and that will get you away from the fender. Depending on the car and the design of the rim, around the 5.72" backspace mark is where you start having to pay attention to tie rod clearance. With a 17x8 and a 245/40/17 or 245/45/17 I'd probably want between 5" and 5.5" of backspace to be safe. Less means you'll have to watch the fender clearance, more will mean you'll have to watch the tie rod ends.
Yeah I did a test fit on my '74 Duster with a 17x9" with 5" of backspace and a 275/40/17. I needed a 1/4" spacer to make it work, but that was all it took. Plenty of room. Dart's are a whole different ball game, smaller wheel tubs for sure. You need the 1/2" hanger and shackle offset kit to fit 275's and 17's of bigger on the back of Dart. I physically wedged the same 17x9's and 275/40/17's on the back of my '71 Dart, but as I mentioned already, it hit both the quarters and the springs. I got the wheel in place, but you'd never be able to drive it.