Matt,
If you want to keep the stock covers, just get a set of valve cover spacers to raise the height.
Here's one source at Jegs;
http://www.jegs.com/i/B-B/128/63920/10002/-1
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.