Here in California it is very hard to find good heads. If you have access to a pressure tester to check for cracks it would be worth it to stack a crate full of heads. My local source only does a leakdown test on his blocks then sells them as good. I have yet to get a good one from him.
Maybe some of the Injector Pumps from the Turbos too. It all depends on how much you can spend and How much you want to store. The IP for the 1.9 TDI that has been converted to manual seems to be the hot topic on the VW GTD Forum too. You might want to look at their pages for ideas.
http://www.vwdiesel.net/phpBB/God Bless the Military!!!