I would not claim to be anything close to a "Gitzo historian" but I do know that 1325 and 1327 were both models in the Gitzo Mountaineer series.
Gitzo introduced a new series for their top of the line models in January 2012 and called it the Systematic series.
Today's replacement model for something like the 1325 would now be in the Systematic line. I believe the closest thing would be the 3532LS.