318 Four Barrel Intake

340Mopar pretty much covered it,but,if you aren't stuck on cast-iron, there was an "SP-2P" intake from Edelbrock that was a pretty good street intake for Square or Spreadbore carbs. Also, there was the LD4B,an older design and becoming a little hard to find. I think Offy used to make a 4bbl intake as well. As long as the ports are the small ones for the '66 and later 273/318 heads, you'll be fine. You can always paint the intake engine color to try and hide the aftermarket look. Keep checking e-bay and the like and one will show up. The '66-67 273 factory 4 bbl intakes are getting scarce and expensive!!!

Hope this helps...