St or plain zetec Blacktop they are both 0.6mm and the same mls design. The older silvertop has a thicker gasket and is said to be more tolerant to surface finish.

Any way, the guy that has the high horsepower drag fiesta ( ignition advantages ) sells Forged pistons and rods and in the description he lists the Cr against differant hg thicknesses.

0.25mm is a change in Cr of just over 0.1:1. So the differance between 1.6mm and 1.8mm is around 0.07:1.

Now this is a rough and ready assumed calculation but the more I look at it, the more I think I would be just as happy using the cheaper gasket.

If you really really wanted the ford gasket I would sell you mine at what I paid but I am not posting it.