In '68 the multi-leaf spring most likely helped with axle windup, but not as much as the staggered shocks did.

Since a staggered shock upgrade for a '67 is pretty tough, I suggest what I did - and added the factory LH traction bar. Provides much improved wheel hop resistance while looking OEM. The spring changeover will provide less improvement as far as wheel hop goes.

In other words, the dual traction bars will provide the most bang for the buck.