Are you married to the idea of "318 Four Barrel" emblems?
The scoops just used "340" emblems.
EBay is loaded with emblems for the BMW 318i and 318d guys, cheap- self adhesive, just leave the suffix letter off.
Like these:
vs.
Or just go to the boneyard and get a couple...
There's even a 318CI, just tell people it's "cubic inch".