A few years back I went to my local big chain auto parts store and asked the guy behind the counter for a set of 8 AC R45TS spark plugs. "What's your year, make, model and engine size?" he asked. "Does it really matter? I see boxes of them on the shelf just behind your head." I replied. "Year, make, model and engine size!" he demanded. "1970 Ford Mustang Boss 429" I answered. His fingers slammed the keyboard loudly as he entered the info. "Those spark plug don't fit that car!" he exclaimed, looking at me like I was extremely stupid...