[68c10airstream]

In post #3 with the 2 holes close together, these were used to index and hold spark plug wire holder looms. One hole threaded to hold down the bracket and the other hole was used for the loom indexing notch to fall into to prevent it from moving around. The plug wires run behind each cylinder head and then under the exhaust manifold to then come up and "Y" off to each pair of plugs. The wires ran along side the block down low to stay under the hot exhaust manifolds and near the block to be retained with more loom holders.