You are looking at a pair 1976 Chevy 454 cylinder heads. They are cast # 336781 and match dated at E2176. They have 2.06 / 1.72 valves & 133.06 CC combustion chambers. They are the X heads with the higher flow runners. They are oval port. This cast # was used on 73 to 79 Chevy truck, Caprice, Monte Carlo, Malibu and Elcamino with 454. Would be a good choice to lower your compression ratio on an older 396. These heads are cores for rebuilding. They need everything including valves, valve guides, seals and springs. Removed from a running engine years ago but poorly stored. They?ve never been modified. Good cores.