Here's the deal - the oilways don't line up. Check out a side-by-side comarison of a D17 and a D16 block.
And here's a D16 gasket sitting on top of a D17 block.
I'm not saying that you can't mate a D16 head with a D17 block (and I'd think it would be cool) but I'd be interested in how it's done just like everyone else.