Stick to stock plugs, can't go wrong with Delco, or equivalents. Regap to about .040" since don't need smog rubbish and reset timing until it's happier, 18-22 ish. R46SZ is original, or R46S where you set your own gaps. Make sure it's the correct type, nearly every Olds heads or engine I've pulled down has had some variation of Chev or Holden plugs in them, simply because the thread matches, but wide variety of electrode positions.