While I agree with everything that has been said...
It is possible to limit the mechanical advance capability of the Motorcraft (Duraspark) distributor easily.
This can allow you to set the maximum advance of 35* (or whatever you choose), and then still have a 16* idle advance, by only allowing 20* of Mechanical advance.
This is done by shimming the dvance limit stops inside the distributor.
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.