I would go the easy route and remove one of the door locks.
I had this same situation. I just removed the entire steering column and took it to the locksmith. He had the correct blank and made me two new keys. You can remove the ignition switch and similar to the GT you have to drop the column from the dash and remove a bracket. then you can get to the magic little pin to push in to remove the ignition switch.I recently bought a 1970 Opel Kadett LS and it has no key and I cant figure out how to remove the ignition switch to have a key made. So does anyone know how to accomplish this task?
If you are talking about the actual electrical switch, they are the same for Kadett and GT.I wonder if OGTS can rebuild a Kadett switch like they do for GTs. Or could the switch itself actually be the same as used in the GT?