I have built a 1974 zak replica, 2 litre BDG on Lucas etc, I have all the tooling to make an alloy atlas, I am very weight conscious so made all the patterns to remake the atlas.The casting is a bit wider with gusseting resulting in double the stiffness in the toe plane and the same stiffness in the camber plane(I performed bending tests on my alloy atlas and a normal atlas).We used chromoly tubes and the result was a casing 10kg lighter than a standard one.Here is an address of some pis of my car.
http://www.groundsky.co.nz/index.php...ntrantID=16411
Also go to ebay de and buy a copy of raylle racing 7/74 they road test the zak car