1970 340 SPARK PLUG RECOMMENDATIONS

Wyrmrider said
we don't yet know the compression but that extended tip is going to work better in a low compression 340 also
also check out RFN14LY and similar styles for low compression there is/was a colder version available

For those reading that..
longer tip...hotter plug.
Shorter tip...colder plug.

Too hot a plug range and you'll create potential for preignition.
Too cold and you'll fool the plug =blackening of the insulator.