There are certain race cars that use a track bar with leafs, but the problem is the way a track bar wants to move in an arc. So now you have to match the roll center of the leafs or you'll have counteracting forces. I think a watts linkage would be better.
How about Del-A-lum type spring bushings?
I know on my track bar and coilovers I played with mounting locations to tune the ride. But with the coilovers you have to have the track bar. Edit, but after installing the Double tri-angulated rear 4 link i no longer use any track bar and love it. No more body being shoved to the side. To get the roll axis under control I had to make my upper links fully adjustable in vertical mounting locations to control the roll axis for street manners due to no track bar. But since this truck is built more for trails and not high speed turns, I just take the turns easy.