How do I know if I need self-aligning rocker arms or not?

 

If your heads use pushrod guideplates bolted under the rocker studs OR if the heads themselves have oval-shaped pushrod holes that prevent the pushrod from moving side-to-side you want NON-self aligning rockers.

You want to use only ONE method of locating the rocker arms over the valve tips or risk tearing up parts from two locating methods "fighing" eachother.