3946074: ’69 rectangular port, open chamber, 2.19- and 1.88-inch valves, aluminum. Used on 427ci L88 and ZL1 engines.
3946074: ’71 rectangular port, open chamber, 2.19- and 1.88-inch valves, aluminum. Used on 454ci LS6 engines.
https://www.chevyhardcore.com/tech-s...-head-id-0219/