When you posted on FABO that you were running the newere wheels without a problem I was scratching my head because the 5.72 backspace wheels barely fit an a body. The only thing I can think of is try running a hubcentric wheel spacer and putting the stock tierods back on. Hold it did you say all poly bushings including the lowers? I bet the lower bushings are moving around and causing your problems. 
56 Plaza 63 D100 step side 67 Coronet, 68 Roadrunner, 69 Super Bees, 69 Coronet 500 convertible, 70 Roadrunner Post, 79 D150 360, and a severe case of Mopar a,d,d
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