What Depth Spark Plugs? 327 With 962 Heads

[ShortCST]

I'm looking at shorty spark plugs to sneak underneath my Doug Thorley Tri Y headers, and noticing that there are two depths of threads. Will the deeper ones fit? I'm thinking that they'll increase the compression ratio a smidge if they do (by sticking out further into the combustion chamber, thereby shrinking the size of the chamber a bit), with the related benefits.