My father's was a '73 GTS. There were no vents until he had them installed by the factory in 1982, I don't think they do much, my PB remains without vents and looks great!! As for value, several 72' and 73' are for sale in Europe for twice what they're worth here in the US. No idea what they should go for tough, I agree more specific information is needed.
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.