I have no technical know how but I just wanted to throw this out there.
What about a 5M head, or maybe even a 7M head (Toyota), I'm not too sure what all needs to match up but the 5M is a 2.8L strait six out of a Celica XX. Speaking of which the head that TonyD mentioned, which I first saw it I thought 5M. I'm not sure how much the 5M flows compared to the L series head, it has a timing belt though.