First I'd suggest you check to see where the slop is, i.e. the coupler, box-the mounting bolts can loosen up, and even cause flexing on the K member. I didn't notice any problems with my stage 2 box , but have replaced 3 idler arms after installation. I've got 255/50-17s on the front of my barracuda, with a late K-member IIRC '75.
