What block for the northbridge on a DFI P35-T2RS?

I have just replaced my EVGA 680i LT with a DFI P35-T2RS, and my old EK block won't mount of the northbridge. I know that they MCW30 and Enzotech Sapphire will fit, but the whole aluminum + copper thing bit me before and I'd like to avoid it again. Thanks!

MCw30 doesn't have any alumium in it, not sure about enoz block.