Thanks greg. Interestingly enough, the plug that came in my Dorman "kit" is a #555-009 (versus the 555-008 you referenced). Checking Dorman's website revealed the -008 is roughly .020" smaller as compared to the -009. That seems to validate the -008 as being correct given when I set the -009 at the hole, it's not even close to wanting to start in the hole (even with tapping the driving tool with a light hammer.....)