You need a sleeve. The bolt needs to tighten down on the sleeve and the bushing needs to pivot on the sleeve. The bushing should be press fit to the spring. The bushing will need to be wider than the spring (too keep the spring from rubbing on the mount) and narrower than the bushing (to keep it from binding up when you tighten it).
The old rubber bushing was the same, the center sleeve tightened in, and the outer sleeve pressed into the spring. The difference is the rubber bushing flexed when you hit a bump, your will rotate between the bushing and sleeve.
