Several different companies make tools just for removing wiper arms. Here is a link to some on Ebay.
http://shop.ebay.com/?_from=R4...t=See-All-Categories
Your local auto parts store will probably have one as well.
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.