I have been to 4 different parts stores and they all give the same listing for spark plugs for a '67 292. None of them fit. They all have 14mm threads. I did a search on here and found a part number that someone else used and that was no good either. The hole is slightly larger than the plug it is calling for. The casting number on the head is 3864890 and the block is 1970. If that helps. Thanks in advance.
