Re: Need Spark Plugs
An 03 should be a Vortec. If so, you'll need the longer threaded AC MR43LT. The MR43T's are for the pre-Vortec heads. NGK also makes a suitable equivalent in a marine rated plug as well. I don't know if Autozone carries them but a NAPA or Oreillys/Advance Auto should be able to fix you up.