rust on cylinder heads?

I was combing through a junkyard last week when I came across a 98 explorer, and i kind of wanted the P's off of it. When I did a visual inspection, I noticed the heads have a fair amount of rust. Are rusty heads a problem, and if they arent a problem, and will run, would they be worth a damn? or should i just skip this all together, and find a non-rusted pair?
 
Have a machine shop clean them up. They can dip it in some cleaner. You'll need new springs and seals on junkyard heads anyway and to have them checked for straightness.