Suggestions on which plugs to go with

Thanks for sharing!
When I visited the NGK site, I entered “Plymouth Duster 340” to search compatibility and got the response “not compatible with this vehicle”.

Do you think this is because NGK’s compatibility search is using “stock”/OEM specs on the motor. I’m thinking that shouldn’t matter since my motor is a 340 small block, anyhow. Thoughts?

This is the plug I entered in the search option:

NGK 6509 LTR6IX-11 Iridium IX Spark Plug