Wish I could help more on the plugs. I used NGK plugs (8's) up to 200-HP and 9's on anything over that. Keep the gaps tight (between .030"-.035") even if using an HEI.
Check out Ken Keefer's site (Pontiac Dude) at
http://www.pontiacdude.cc as he has tips on reading plugs. Perhaps he or someone else can help with the AC plug choice.