Originally Posted by oldskewel

You wait to see how much material is taken off the heads when they are machined. The machine shop will tell you if they needed to take off enough to require the thicker one.

And BTW, for my 3.0i M54B30 engine I rebuilt last summer, the choices were 0.7 mm (what it comes with) and 1.0 mm (the thicker option when rebuilding). My head was warped slightly (and was in fact the single problem that required the rebuild), but still, not enough was milled off to require the thicker replacement gasket.

I also wanted to get all the parts ready. They sell "head gasket kits" with all the common gaskets, including the standard thickness (0.7 mm for the M54B30) HG. But they also sell HG kits that come with all the stuff except the HG. Kind of funny, but that is why. And you can be working with the rest of the kit until you get the verdict back from the machine shop, and then buy the HG separately.