Most of us are well aware of adjusting bump steer by spacing the outer tie rod up/down (and in/out) on the steering arm or changing u/p , in /out location of the inner tie rod., however, I think your zero bump steer was only in your mind, especially with the amount of travel a dirt cars suspension sees. The only way zero bump steer would be possible all the way thru suspension travel is if the three arcs (UCA, LCA, tie rod) all have the exact same length / radius.....and that, my friend , does not exist in our Mopar street cars.