Have a 468 with 11/1 comp. 781 heads,280h cam and a tunnel ram with dual holleys, which a/c plug should I be using or will the ngk perform better?

781 heads use a taper seat plug. For your compression I would (in the AC line) personally use a "4" heat range in an AC plug. I also like extended tip plugs. So.... I would start with an AC R44TS plug. You might go one step colder to a "3" heat range. This would be an AC R43TS. Don't know how a tunnel ram affects plug selection though, as I've never ran one. If you choose to run a different brand plug, the parts store can cross reference the AC numbers for you. Hope this helps.

Wooderson is on the money!

I have used both R44T and R43T at 10.5, either will work. If you're sure it's 11:1, go with the R43S.