66 Dart GT HT Whatsitgonnabe?

Looking in to what you write, I came across this article in Hot Rod magazine where they do a center section swap.

In picure 8, they show this:
http://image.hotrod.com/f/9301190+q80+re0+cr1+ar0/p5779_image_large.jpg

I have one of those in my pile of parts! Should I install it? Or does it only go on after the drive shaft?