[Chipper Chapman]

Heads are a regular oval port, but they don't have your typical 396 closed chamber, thus giving the 265hp a lower compression as well. They were likely the first of the open/semi open style. I saw a pair once and the chamber resembles that of the 71-72 820 and 292 heads, unshrouded a bunch around the exhaust valve. 14.92 weight break for a 2 door biscayne means you could get one of these up as far M-N/S lol