I did use the RTV silicone as discribed by Bosswrench and also suggested by Steve Wilkinson at the time I bought my gasket and it does not leak.
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.