The first thing that you need to add to a 318 is dual exhaust, whether you run stock exhaust manifolds or headers... Your choice... You can use either 2 1/4" or 2 1/2" diameter pipes...
2 1/2" will give better flow, but be harder to fit... 2 1/4" is good for a mild 318 and will be fine, and will also be good with some mods...
Then I recommend going with a 4 bbl and dual plane intake... Get the Holley or Edelbrock 600 CFM square bore carb and go with a dual plane intake like an LD340, Wiand Stealth, or Edelbrock Performer RPM (not the plain Performer - those are junk)... The Wiand Stealth dual plane intake is a nice one also and still available brand new...
The stock 2 bbl carbs tend to wear out the accelerator pump too fast and I get sick of replacing them... 4 bbl is much more reliable....
The 4 bbl will maximize the benefit with the dual exhaust and the electric choke is very reliable on a daily driver even in dead cold winter... Hook it up to a proper 12 volt source and adjust it properly... Go out on a cold winter morning in 20° pump the gas twice and crank it over... When the engine starts and gets to full oil pressure, put it in gear and drive away... It won't bog or hesitate even cold when the electric choke is set up properly....
The third thing to change on a 318 2 bbl is the timing chain... Throw that junk nylon tooth single row timing chain out and replace it with a good double roller timing chain... You will gain up to 2 MPG if the old chain was worn enough and also when the nylon chipped off the timing gear, they were more prone to jump a tooth...
While your'e in there changing the timing chain, you may as well throw in a better camshaft... Something mild, like a stock 340 cam or slightly bigger, but not too radical...
Then you will have a nice running daily driving dependable 318 that can scoot when you want to and still get some reasonable MPG....