GT40p Sparkplugs....what ones for boost?

For my gt40 heads the stock plug in an NGK is a TR5, I ran a one step colder as I have a bottle that made my plug a TR6 (they are backward in numbers from everyone else). In order to go 2 steps colder you have to get irrid.(sp?) plugs and that is a TRi7. I called the NGK tek. number and they said they do not make a copper TR7.

You would prob. want to gap the plugs alittle closer to 35-40ish, but I will wait for the blower guys to step in on that.