i've got 595 on the rear, they were cheap and were supposed to be for skidpan, not too bad dry, wet fine for normal driving, i'd take a kumho over a federal in general
if the tie rods were adjusted to same toe settings then the rack would be the same length so shouldn't change anything, what was the report from the alignment?, otherwise hey you say they're the wrong ones & the car feels crap, put the right ones on?
stock exhaust with decat is all i'd do, also the multivalve gives a brutal twang haha(which turbo muffles), thats why even sohc rb sounds better than dohc with exhaust, the 4l falcon is prob not a multivalve model?