Finding the right spark plug for your 340 or 440 HP ..

If you go to the parts store and ask about plugs for classic mopar or street rod 340 - 440 - 383 etc your probably not going to get the right plug from the parts guy and usually to cold ., If you ask about Heat range forget it ..
Numbers ? some higher numbers mean colder in some brands and some lower numbers mean hotter plugs which do you choose ? :prayer: