What impedance were the old speakers, and what was the impedance of the total cabinet? That will provide the answer to your actual question; however...
Most 412's are wired series/parallel and the total impedance is then the same as one of the individual drivers, and if your 412L was wired that way you will end up with a 16 ohm cabinet if you just swap drivers. Your options for using four 16 ohm speakers are either 64 ohms, 16 ohms, or 4 ohms total cabinet impedance.
64 ohms is pretty much impractical for most applications, so your choices are basically 16 ohms or 4 ohms.
What are you going to use to power the cabinet, and how many cabs are you going to use?