Put a set of heavier bars in from a 340 car, or new heavy bars . Get rid of the bounce. I had /6 bars in my car for drag racing. It would bottom out on every dip in the road on the street.
Because the smaller bars take more wrap to get the car to ride height they create greater lift on acceleration. But they also compress much easier. V8 or 318 bars are not much better.
the factory numbers are as followed
/6 ---------------888,889
318 --------------890,891
340---------------892,893
68 340 4spd-------894,895 come with heavier stabilizer bar
67-69 383,440-----894,895 come with Standard bar
Now this is only what I have seen stripping these cars over many years. Some may not agree because the info they read states different. The new bars sold today I believe are much better then the older parts including Torsion and stabilizer bars. . Hope this helps steve