If it were me, I would stop buying the same MC from a certain vendor and call one of the Alfa specialists above and buy from them. The ATE cylinders seem to have a drop in replacement.
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.