Foose 17x8 4.5 bs on 67 Dart ?

Everything is too wide. A 17x7 with 4" of backspace and a 17x8 with 4.5" of backspace are both 0 offset rims. The wheel is in exactly the same place, just one's narrower. Meaning, if you run the same size tire the wheel clearance will be almost identical, the only difference will be whether the tire is slightly stretched or compressed on the rim. BBP A-bodies had a +6 offset from the factory, and in the back the best fit is usually a +12 for a BBP 8 3/4 (remember no BBP A-body 8 3/4's, the BBP axles add a 1/4" or so).

In the front a 225/50/17 on a 17x7 with 4" of backspace will stick out .1" past the 275/35/18's I run on my Duster. That's not much and they will probably fit as long as your car doesn't sit low, but it will be tight. I have a little room to the outside on my car, but it's not much at all.

In the back I just don't see it. All of the Dart's that I know about that are running 245's with stock spring locations and BBP axles are running 5" of backspace on 8" rims. And your rear disks add another 1/4" to 3/16" compared to the stock drums, so if anything you need more backspace than they have.