[thabaer]

Unless someone made changes or your '77 is not like my '79, the only difference is a groove down the length of the key. The valet and masters are cut the same, the difference in my keys being an extra groove on the master. Check with a dealer or knowledgeable locksmith about this, you may just need to have a key made.

Do NOT assume you need to change any tumblers until you have verified that you don't really have a valet key.