670 were a closed chamber?
Were they also a 22 degree valve angle head?
That would mean the piston valve reliefs will need to be 66 style and back. Also the 22 degree angle heads use shorter pushrods.
Better do some more homework before buying .
The 67 326 still used a 22 degree angle head, and pistons that were reliefed for them, I am not sure about any others.
Fact is stranger than Fiction