What can happen if you get a set of spark plugs that are too cold of a heat range?

they will foul up.

Ususally on an NA car you dont need colder ones.

why not on a n/a car?

most of the mods on an NA car deal with taking away heat from the engine, while with the SC you end up adding heat when you go down in pulley size.

Didnt you guys read that Spark plug sticky at the top of the page?

No I didn't. But I was wondering about this because when I get the GTP, I will be modding it, and I was trying to decide between 1 or 2 heat range colder spark plugs with the following mods: 3.4" P, CAI, 180 T, R/T DP

For those mods i would only do 1 range colder personally.

i concur. One heat range will be fine. I think ZZP or intense have a list of mod "steps".

I've read all the vendor sites, and I've heard people go both ways on this. Some go 2 steps colder, some go 1. I'd wanna go 2 cause I'm afraid of KR, but I don't know what will happen if I go too cold.

If you want to go 2 steps you will be fine, You've read it. I guess if you wanna go further then those mods in the future just invest in 2 heat ranges colder, Keep in mind you'll have a smaller spark on those NGK TR6'* if that'* what you're gonna run, which MAY decrease power slightly.

Every L67 is different, some cars just have more knock. Some don't.

Maybe I will start with the Autolite 104s (1 colder). If I am still having too much knock, I can try the 103s.