Do they make a colder plug than autolite 103's?

[OrangeMustangGt]

Im looking to turn up my boost, and if possible would like a colder plug. Stock gt40p heads take autolite 104's. I have been running 103's, and i know they dont make a colder plug. Is there any other brands that will work, and be colder? anyone know of a cross-reference?

 

[BlackVert]

not sure if this helps or not, but i know that autolike 23s are 2 ranges colder than stock

*edit* but i have e7 heads, not gt40ps

 

[SVT3183]

check this thread at corral: http://www.corral.net/forums/showthread.php?t=436174