Could have been, which would explain the choke linkage difference. How long is your choke linkage from center to center? Not sure if I still have the one from the 318 to check it against, or whether I sold it along with the carb.
EDIT: Just brought up my eBay pictures. Looks like I sold it along with the carb. Grrrrrr...
At worst, swapping the carb studs isn't difficult at all.