Replace the original terminal block. They turn into a disaster with age. They aren't so great new either.
http://pantera-electronics.com/wireharness.htm
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.