[DMXF]

Guido36, first of all whatever Wouter Melissen states on that site is tainted by his use of the word "alloy". While some people associate it with meaning aluminum, look up the definition, alloy simply means there is a mixture of different constituents in the metal. Steels are made in different alloys.

The first GT40(s) in '64 were fitted with the all aluminum Indy engine, which is different in virtually every aspect from the engines installed in Cobras. When Shelby was given the responsibility for fielding the GT40's, as part of his changes he pulled those engines and installed his cast iron Cobra units.