I think the stock rocker arm ratio is 1.73 to 1. To change the rocker arm ratio it seems to me you would need to get a rocker arm with a different fulcrum point. I would think that would require some very special parts and the expense would be difficult to justify when you can just change the camshaft to achieve the same result.
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.