Sure the flat 12 was very succesful, but nothing can beat the sound of their V12. I last heard it in Belgium 1995 and just the memory of the sound sends cold shivers down my back.
I believe Ferrari had a 3litre V12 in development along with the V10 in 1997-1998 and rumors are it was more powerful that the V10 without the outrageous fuel consumption of the ones from the early 90's. Then suddenly V12's were banned.
And yes, 333 stands for the displacement of a single cylinder. Same goes for some other models such as the 456 (also V12).