Crane says for the st.......1988 and later engines equipped with self-aligning rocker arms require the installation of pushrod guideplates and appropriate heat-treated pushrods in order for these rocker arms to function properly. Valve cover clearance must also be checked. dont have to have them on older motors.

comp. cam says.....1988 and older chevy. dont have to have guide plates. probably wouldn't hurt anything though.