Pantera Performance sells bushings made from graphite impregnated polyurethane. Apparently, they do not squeak but they are harder than regular polyurethane bushings.
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.