Hey guys, I've got a couple of possibilities for a 405 head in my for sale thread here: http://ozvolvo.org/discussion/2191/the-great-redblock-engine-sale#latest
There is the head with manifold attached which needs to be rebuilt, going cheap as is, or I would be willing to strip it down and sand blast it at extra cost, to give the machine shop a good basis to start on. I haven't got much spare time at the moment so it could take me a couple of weeks to do the work.
I'd also consider separating the head that's on the engine at the top, it's cleaner and seems to be in better shape.
I don't have any 531's available at the moment.