Well my engine builder pulled my old motor out and bagan to disassemble it and pulled the heads off to inspect. Well guess what, one of my heads has the 4 thread holes and the other has the 8 thread! Now from what I know when I bought it from Carmax 2 years ago it had a clean history and checked my VIN though Ford and it has NEVER had warrenty work. So could Ford have installed a set of 4 thead heads from factory? I dunno, but seems fishy to me. Just thought I would let you all know and to double check your 03-04 heads to be sure. I'd hate to see someone blow a spark plug out on their 03-04 L thinking they have the newer heads. My build date was in March of 2003.