Will these 17" wheels work on our Dart?

Appreciate your input. What's your thoughts of a spacer in the rear, not sure if I'm a fan but don't have any experience with them to judge.

Spacers aren't a big deal. For just a plain flat spacer I don't like to go any more than 10mm thick. That's just me and my personal preference. To go that thick you need longer than stock wheel studs anyway, so you're not dealing with 40+ year old wheel studs either. If they have to be thicker than 10mm, I jump up to 20mm and use a spacer/adaptor that has its own lug studs, like this...

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2pc 20mm Wheel Spacers | 5x4.5 to 5x4.5 | HUBCENTRIC | 1/2" Studs | 5x114.3 | eBay

That type comes in widths up to like 3" for some of the offroad guys. I dunno about how great an idea that would be, but I've run them up to 1.5" thick on 4x4's with 33's and 35's with no issues at all.

You want to try and stay hubcentric if you can, but tons of aftermarket wheels aren't. Pretty sure there's even factory cars that aren't. That's a different argument anyway. As for the spacers, they're like anything else. Do it right, use high quality parts, properly torque the lug nuts and check them for tightness periodically and everything should be fine.