Larry, good news, the 3rd vent is made of sheet metal and then covered with leather...here is a detail (with one of the typical 2 vents to the left...)
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.