Joe,
Sounds like a repair at some point. I've never seen the
rear brake line joined in the location where the valve is.
I hope someone didn't bypass that valve, if it was originally
there.
One clue to look for: Look at the location on the outer
drivers frame rail and see if the mounting location for the
valve shows any signs of one ( valve ) ever being mounted.
The hole for the self tapping screw should show signs of
threads at least.
I would think that an 05D car would have the valve in question though.
Steve