Even if the BMW bore spacing and bolt head pattern is the same as our six, the problem with the BMW head is that it's an overhead cam design. It would take quite a bit of machine work to install a timing belt onto the front of a US Ford six. You'd be better off buying and shipping an Aussie OHC 4.0L six over here.
The pieces needed for the 200xflow conversion from Australia are the alloy head, valve cover, stock cam, intake and exhaust manifold (the manifolds could be optional if you're good at fabricating). The rest of the parts needed for the conversion are sourced locally. If you consider that any used head and block needs machine work, that cost could be part of a normal rebuild. I just did a quick calculation on my cost of acquiring all of the pieces for the conversion (used alloy head, used alloy valve cover, used 2Bbl intake, new cam, new valve springs, new lifters, used header, and head gasket set) and it came up to less than $900US, shipping included (half of total cost).
I believe Jack just wanted to see if installing a crossflow alloy head onto a US 200 could be done, since he had the parts. He was successful.
Mike with Classic Inlines wanted to improve the performance of our sixes. He was also successful.
After all that I said above, I agree with rbohm; the best deal is to purchase the aluminum head from CI. I have one of these too.