There was a thread somewhere here where the side marker lights used a plastic cover, flush with the body, which was painted the color of the car but the light was visible. The guy who did it wasn't willing to disclose the secrets behind it though.
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.