I just got my 04.5 yesterday and I am anxious to get started with the toys. I am looking at the grill inserts and I was wondering if I need one for a 2004 or a 2005. I guess I should know the answer but I really haven't paid any attention to the differences. Also has anyone had any problems with air flow while using one of these?

The 2004.5 truck is actually a 2004 model year vehicle. GM changed from the LB7 Duramax engine to the LLY Duramax engine during the middle of the 2004 model year run. The 2004.5 name is just an unoffical way to distinguish a 2004 model year LLY from a 2004 model year LB7.

The grill change took place starting with the 2005 model year on the Chevy. Chevy returned to the bump in the hood on the HD series, and as part of the change, redesigned the grill.

So, the grill on the 2003 LB7, the "2004" LB7, and the "2004.5" LLY are all the same design/style. The 2005 HD truck grill is different.