Dodge Dakota after market headers on a 65 Barracuda

On a 273 I wouldn't overly worry about it, unless your engine is pretty built with lots of overlap then you'd want longtube headers anyways.

Here's a manifold and headers shootout on a 5.9L 300 hp crate engine.

https://www.hotrod.com/articles/mopp-0307-installing-exhaust-headers-into-300hp-crate-engine/