on the majority of street driven small block HDK builds, a 12" 300 lb rate or 325 lb rate spring does the job (Qa1 #12HT-300 or 12HT-325). Be helpful to know the installed height (eye to eye) of your shock mounts and the specs (compressed / extended lengths) of your current shock. If you have the spring out....also the full length of the coil spring.
