I just uploaded a file called IIpost (the name was supposed to be
Ibn_Ishaq_Isnads but I don't know how to change it now) to my google
group called "Islam Origins". It contains all the isnads in Muhammad
bn Ishaq's "Sirat Rasul Allah" arranged by narrators names. There are
379 names involved. The name that occurs most often is al-Zuhri.