The guessing game is not the answer.
1. Where did you get this chewed up seal? Does it come close to fitting the timing cover?
2. What are the numbers on it? I see the word National. It WILL have a number.
3. What is the ID, OD, height? I have those dimensions but don't want to influence your measuring.
4. What part numbers did you order, from what vendor?
If you answer these question we will tell you what to buy...IF YOU NEED A TIMING COVER SEAL........ That's what it's called.
Rockauto and other vendors do mix up GMC part numbers. They give straight 6 and Chevy 305 V8 parts. ALWAYS buy from a place near you, if you can (no ship), and ALWAYS buy where returns are accepted when buying 60-66 parts. ALWAYS ask here first and check the search function. Jolly's legacy page has a "Known Good Parts" section. No one knows anything anymore about these motors but us. Parts guys just wing it.
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