Buried in his post, “stock looking engine, these are going on an original m code dart” that’s a factory 440 DART SWINGER. so I bet iron heads are what he wants.
use the 906 heads. Are you using stock manifolds? Then you don’t need oversized valves.
No,,, I will run under chassis headers… have only left hand manifold but I realize they are too restrictive,,, have spoke to the original owner and when he put fender well headers on it ,,,,, it way way stronger,,,, it’s a rare m code 440 gts