What spark plug should I use on a 408 stroker?

[Barracudadan]

I`ll be having my motor dropped in this weekend and my mech wanted to know what heat range to use on the spark plugs. He said he couldnt get his socket to fit in the opening for the plugs and might need smaller peanut plugs. I gave him some NGK plugs which I thought were from my 360 prior to it being rebuilt they were like new. I now have a set of Indy iron X heads not the stock heads anymore maybe there isn`t as much space in there  anyway I could use a few suggestions on what brand/heat range plug I should be going with on a 408 stroker motor with iron indy X heads and a mancini electronic ignition. Car is going to be used on the street only.

[Chryco Psycho]

I would contact Indy , they should have a proper # for a spark plug for he head .
 I would also stay away from NGK , they foulf very easily , I have had better results with any of the cheaper plugs , Autolite or Champion etc