They're ProComp heads - and they're this new style of head; maybe you've heard of 'em... They're for LS1's

JFWY dood - I couldn't resist!

Definitely their is a possibility that I can get a socket shaved down to fit into the hole. But WHY BOTHER? It's like the continuous saga of avoiding the obvious... If it were JUST the issue w/the spark plug - I could see going thru the trouble of shaving a socket to fit the hole... However; it's not!