I was discussing this recently with my locksmith friend, and he said that the 95-up double sided key locks have to have the tumblers in the lock cylinder line up correctly on both sides. I know sometimes we have to wiggle the key a little bit,to get it to work, on both trucks.....
When we got the Burb ten years ago, the ears were broken off the ignition switch lock cylinder. Dad got a replacement cylinder and had this guy rekey it, plus make some more keys. So everything on it works with one key as it was designed to do. However on Rawhide the crew cab, the ignition lock cylinder was replaced before we got that truck. I suspect the ears got broken off; I understand this is a common thing on these trucks. So we have a key for the ignition and another key for the doors, but both with the same style key! And they will not interchange. One time when we were using both trucks, I put the key for the Burb, in the crew cab door, and it worked.....but the Burb key won't start the other truck.
He also said that the blade part of the key for the 800/NBS truck, is the same as for the 95-up 400; the head is what's different. Wonder if GM made the key head(what you hold onto) bigger, to make it easier for use when wearing gloves....