on the 75 442 is the opera window plug removable?
 

While restoring my 75 olds cutlass supreme, my car was ordered from the factory with a 442 interior which we are cloning out to a true 442. While in the process of removing the landau top to do body work, I noticed what appears to be a factory plug covering the area behind the opera window. I then removed the interior panel in the interior side of the other window, the glassn goes all the way back like the 442 glass,,,

Can I remove this plug, and if so, is the rail preformed liked in a 442? I am wondering if i can figure out if they took a 442 body and plugged the windows

Thanks
Chris