Excellent. I'll pick up either the Kroil or the PB Blaster tomorrow.
Once you do get them apart, reassemble with anti-seize compound. This kind of sticking is what anti-seize is meant to prevent.
If you can warm the aluminum, do it. You don’t have to get it red hot. If it’s easier, you might be able to heat the whole shebang in an oven then apply dry ice to the fasteners to shrink them.
http://www.samsmarine.com/forums/showthread.php?14083-Stainless-Bolt-Seized-in-Aluminum