With large files, sometimes it’s easier handling them split into many smaller files. In order to rejoin the files one typically uses a file joining program. I came across two that could possibly perform file joins: MacHacha and Split & Concat.
Turns out that MacHacha has some issues, perhaps related to Leopard, as after reaching the last file of a 75 part file series, it simply hung on searching for the next part (which didn’t exist).
Split & Concat on the other hand, handled the files without issue and has the option of specifying the output directory though the Options button before the start of a join session.
My vote goes to Split & Concat for file joining software on Mac OS X.