short ngk or ac delco plugs?

[superwade57]

I have a 1970 355 mild built with gm 882 heads I'm looking for an acdelco or ngk plug with an equivalent length to the accell shorty plugs for headers. I would prefer a plug in a heat range comparable to the ngk #6 or #7... probably 6. 7 may be too cool... according to what I've seen. Is there an issue with to cool? I know too hot has many problems.

I know plugs is covered a lot but I've searched and can't find a definite answer.

Thanks.