273 upgrade to 4bbl?

Ok, I have found a part number, and it is a Offenhauser with everything on top ground off. BUT.... the listing I found on Summit for it, shows that is it for 64-65 273, which if I understand correctly is NOT an LA motor. So this will not fit my car?

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Is that a #5489? Will a 3/8" bolt fit in the bolt holes?