As far as I know, the flat bar was offered as a dealer installed after-sale fix for instability complaints. I have little evidence to support this claim, other than 'I've heard a lot of dudes say so'.
The overall improvement in handling for my car was nothing less than dramatic, from positively frightening to positively in control. Of course, replacing a badly worn front suspension and adding a upgrades at the same time makes it a bit difficult to differentiate which made the most difference. New springs (AC rate front, six leaf rear), shocks, control arm bushings, ball joints, and the crank eliminator were installed first, all at once. Abrupt stops no longer require fighting the car to keep it from diving for the ditch or the oncoming lane of traffic. The drag link, tie rods, and roller idler tightened up the manual steering nicely, though I still need a rag joint. Understeer really increased with the bigger (1") front anti-roll bar, that was improved by the addition of the (7/8") rear bar later. I still have some understeer when I'm playing around but that's arguably due to the 275 rear/215 front tires. Body roll is minimal, ride quality was improved.
I purchased some urethane bushings for the front spring eye, but haven't installed them yet.
