Spherical leaf spring bushings

If you are talking about "oval" bushings like F-bodies have, I doubt it would be worth the effort. That was part of Chryslers effort to soften the ride. Racers preferred stiffer bushings or aluminum inserts. I believfe OEM F-body front bushings had 2 holes in them that racers filled with a bolt to help stiffen them in the early days.

Roller bearing bushings would be helpful not only for stiffness but for their reaction. I've heard of some racers putting them in the front & rear leaf spring locations, but very expensive.