Track first. For the track that falls on the split, just name it track##a and track##b and recombine later. You won't be able to combine the complete files from the 660 in most programs. However, depending on the software you're using, if it allows for files > 2 GB using some other format, you can create a new file and paste both of your 660 files in sequentially. For example on the Mac, Spark allows this with the w64 file type.