Well, I did a little research. For those of you that wanted the solid rear quarter panel...but weren't able to get it, you can get them from gmpartsdirect.com

The part numbers for the driver and passenger side are

25825370 driver's body side
15942502 passenger's body side

Not sure how much of a hassle it would be to swap or what a body shop might charge you, but for those that want it....Here you go.

I actually might do it sometime in the future!

 

Yeah, that's a WELDED piece of steel for the whole quarter. Structurally, you're better off filling in the window area with a sheetmetal patch.

 

My body shop would not fill in the area because of the structural change, but this puts new light for those who want to change.