CAESAR II is updated to utilize the rules from the most recent edition and addenda of the piping codes. We do not maintain old codes except for that 1967 Edition of the power code. At the time, the '67 code looked a lot like B31.3. It was the following Edition of that code introduced major changes that make it work more like it is today. Back then, the codes didn't change as fast as we see today and there were still a demand for the older code. Piping programs of the day maintained the 1967 code for those users who wanted it. (My Dynaflex manual of 1979 states that B31.1-1967 Ed. is applied if no piping code is specified.) CAESAR II mimicked that choice even though few, if any, users cared anymore.