Duster 1973 with 15X8 inch wheels front and rear

My backspace is 4 1/2 '' on those 15 X 8 wheels

The narrowest tire that's going to fit a on a 15x8" is a 225/60/15, and on a 15x8 with 4.5" of backspace they'll still stick out further than the 275/35/18's I have on the front of my car. Even those will probably rub, and they'll still look a bit stretched on a 15x8, which isn't a good look for a tire on a 15" rim.

If you're serious and you want this to work well and look right, you should really find a set of 15x7's. The 15x8's you have are fine for the back, but they're going to be a headache on the front. Sell the 15x8's and buy a set of 15x7's, way easier in the long run.

4 1/2" is perfect, same as I had. throw 1 on and see

No, it's not. With a 245/60/15 on the front like you suggest that tire will stick out past the lip of the fender. Not to mention that's a 26.6" tall tire, where anything much taller 26" causes clearance issues when turning. I suppose if you run it jacked up like a 4x4 it might clear. But at that point you should just sling a dana 44 under the front and go wheeling like this guy...
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Yeah, sure, I'm being dramatic. But you're going to need a couple of inches of air space between the tops of those tires and the fender lips if you don't want them to ever intersect (rub). And that will put the front way up in the air, it will sit up as high as the back does. And that's not a good look, even if you're a fan of the big 70's musclecar rake.

Your car looks great the way it is. Just get rid of all those window stickers, and you have a winner. I run a 15x6 with a 205/70/15, no rubbing car drives wellt handles fine. It is a Duster by the way, not a BMW. Dusters were not build to be a road race car.

Ha! Dusters were built to be grocery getters for little old ladies. The 340 options were out there to just build interest so they could sell more /6's. They certainly weren't built to be drag cars either! If your lack of imagination and understanding of suspension theory limits you to thinking they're only good in a straight line, it's your shortcomings that are the problem, not the cars. Mopar did just fine in the TransAm and AAR series, and a Duster will handle just as well or better than either of the larger E body Challengers or Barracudas they used for those series.

And it doesn't sound like the OP is trying to go road racing anyway. Just put a wheel up front that won't push every time he turns the wheel at speed on the street. You know, so he can safely drive it on actual roads with reasonable assurance it will actually turn when he needs it to instead of push straight on those frontrunners.