'67 hardtop automatic 400 with mild mod's (maybe 375-400 hp), going from an open rear to 3.55 posi this winter.

Right now I have the original single leaf's with the right side traction bar only.

Am I better to go with new single leaf's and add the left side traction bar, or convert to multi-leaf and no traction bars? Are the traction bars really not necessary with the multi leaf springs for this kind of hp with a posi? Or multi leaf with the single traction bar I already have if it still fits?