PB blaster is your friend. Soak it, bang on it a bit, soak it some more, get a burger, come back 20 minutes later with a pair of the biggest vicegrips you can find, take a hit of PCP, yell a curse at the UAW for underengineering their crap, and yank that sucker off.

For extra torque, use a pipe as a redneck wrench extension.