I just completed the same Job. -Not fun. If you remove the cotter key and clevis pin from the master cylinder pushrod and the one other (not the pivot) in the assembly, it will allow you to rotate the arm that is preventing removal just enough to do so. Reassembly goes the same way. As you already know, it's very tight working under the dash. My driver's seat was removed. -Good luck.
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.