Thread: 1963 421 Block Help
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Old 06-24-2026, 10:26 PM
1963cat 1963cat is offline
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Join Date: May 2023
Location: Muskegon MI
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its a 4 bolt main and looks to be large main and rf corner near deck looks to be 421 i would say. I will check casting number on mine to be sure but looks to be 421..

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