318 head flow

Depends on the amount of time, money, and abilities. My go to method for any Mopar iron head goes as this.

Core drilling the heads for .5" bronze guides.
Grinding the lead in of the intake guide completely out, like it was never there.
Gasket match intake ports to 340/360 size. Eliminate valve cover bolt bumps. They will break through, don't worry about it, use thread sealant on studs to seal.
Create a trailing vein with the back of the guide boss so that the air doesn't eddy around the back side of the guide.
Profile the bowl and roof of the exhaust port.
Press in new guides and hone to size. .0016 on the intake .0018 on the exhaust.
Cut new intake and exhaust seats, open bowls with 75° cutter, and deshroud cut chamber.
Blend bowl and profile short side.
Blend chamber deshrouding cut using sacrificial valves to protect seats.
Resurface to target CC volume. 6 thou per 1CC

This process is involved and costly to say the least but yields great results if you're targeting max effort gains.