There's a tech tip somewhere that gets referenced pretty much every time this question comes up. I suppose somebody will post a link to it soon. Basically, use the 261 head gasket as a template and mark the steam hole positions with a transfer punch, then drill the holes at a slight angle with the bit pointed toward the center of the head. I think it's about a 10-15 degree slant. This helps the hole intersect the entire coolant passage above the head deck instead of just getting a partial flow.
The reason for the holes is the same one that requires steam holes in a small block 400 V8 head- - - - -no openings between the siamesed cylinders for coolant to flow. Without the holes in the head and the gasket, steam pockets can develop where the cylinders meet at the center of the block.
Jerry
