How about a head off a engine for an anvil? 

Not sure if you are talking about the cylinder head or the engine block.  Both of these are cast, as far as I'm aware, and typically not of ideal materials for anvils. The configuration doesn't seem to lend itself well for an anvil either. If the former I believe that most are relieved as much as possible behind the face to reduce the cylinder weight for efficiency.  If the latter there just aren't many flat surfaces and the weight is distributed poorly for use as an anvil.

You would do better looking for old fork lift tines in the scrap yard, end mounted rail sections, or large, solid drops of mild steel.   Of course virtually anything can be used as an anvil in extremity,  but some things will function better than others.

What he said.