Anyone know what that piece is called and where I could find one?

thx. BJ

 

It's called the "Trunk End". Here is the factory service manual section that has it listed. You can't buy it new any longer and 1979/1980 are unique but that later model ones will work without any modifications. The big difference is that the later models has a light.

https://www.foxed.ca/rx7manual/manua...700A-6930A.PDF

 

I have one in decent shape (last I recall) if someone has a 3d scanner and printer.

 

The 79 cover is a one year only part. The 80 is longer, like the FB's, only without any light. I believe all the later ones will fit a 79, but the rear, hanging carpet for the longer covers is also different than the carpet for the short 79 one, so you may need to also use the appropriate carpet to go with what ever cover you use.