Frozen Spark Plug

Hi everyone. I'm working on a set of 308 heads that have never been touched but have some rust issues. One plug is frozen in the head and rusted badly. I've got the plug well filled with PB Blaster and I'll give it a day or so. Is there any way to get the darn thing out?? The socket doesn't fit, too badly corroded. I can't believe how these heads rust!