what is truly amazing is GM used very similar ignition switches up thru 1990 on P30 vans.
the flats for the D shaped hole are in different spots on the later versions. but there is enough room to file a new flat to keep the alignment. the connector pigtails have a slightly different shape but the terminals can be moved easily from the early connector body to the new connector body without having to recrimp them.
working in a cadillac restoration shop in the 80s.. the bosses had a big box of GM keys . they would get a car in and find keys that fit and leave the keys with that car.. cutting down on the box of keys.. i finally got them to let me figure out the depths and cut new keys by depth and put the originals back in the box..
somebody threw away my list of 102 try out keys for GM locks decades ago. long before i worked at the caddy shop.. at one time in the late 80s, we had 7, 59 Eldorado Biarritz convertables in the shop for restoration .. just thought i would share..