Mopar didn't offer 4 barrels on the LA318 until the late '70s. But I believe these motors also used 360 heads so the port of this intake will be larger than the ports on your 318 althought it will still bolt on to your motor. These intakes use the spreadbore type carb like Thermoquads or Q-jets.
If you find a 4 barrel intake off of a '66 - '68 273 it will match the ports of the 318. These intakes use a squarebore carb like a Carter AFB/AVS
Chuck