How much time and patience do you have? I did an entry door tumbler key with a file for a '64 avion. Remove the tumblers assembly, find the right key blank, by more than one blank for mistakes. Insert the blank, observe the tumblers on the OUTSIDE of the tumbler assembly, measure blank and file to match one tumbler at a time. Again and again until you get it right. About 2 hrs and a pot and a half of coffee. Resist the urge to remove and file the individual tumblers inside or outside the cylinder to match your key. That usually ends badly.