Some of the truck manifolds from the "Magnum" series engines do flow well. Not nearly as well as headers but still better than standard 318 units.
The 1992-1993 Magnum manifolds had a 2 1/4" outlet. The right side clears an A body. I've used them. They exit over and behind the oil filter. The right side is an excellent unit because it eliminates 2 bends and allows for a 2 1/4" or even a 2 1/2" head pipe with just a 45 degree bend when turning to run under the floor pan.
View attachment 1716023433
The left side is always the pisser.
The truck manifolds might fit with manual steering but the column jacket will likely need to be trimmed. I ran a 68-71 340 manifold on the left side.
View attachment 1716023434
The damn steering box is the main obstacle there. The options are an upswept design like the standard A body units or a 318-360 mid 1970s manifold that needs some grinding to clear the steering box.
