Marino Perna of Pantera East tooled up and had some made, but they're not cheap. He also had a 0.655 gear ratio made up for the ZF, which makes about the same percent change but only for 5th gear. This is another option.
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.