The '74 BBS comes closest to direct drop-in; that's truck carb numbers 7044s and 7045s. (manual and automatic transmission); van carb numbers 6583s and 6584s. Pics here and here. The 6218s is a '71 Dodge truck carburetor, lacking the built-in throttle return spring and having the earlier-type throttle lever configuration, and no idle kicker solenoid. None of this is a dealbreaker; you can use dual external throttle return springs instead of one external + carb's internal, and you can adapt to the earlier throttle lever. See this thread for kickdown options, and here for how to hook up the fuel vapour canister.
