Sometimes just putting the trans in High and hitting the starter with the clutch pressed will break it loose. If there's a cover on the bottom of the bellhousing, pull it off, and with someone holding the pedal down, try to pry the disc off the flywheel with a knife or screwdriver. If that doesn't do it, you may have to unbolt the clutch from the flywheel. If it were mine, I'd start it in Low gear and shift it through the gears to High, then hold the gas to the floor and jam the brakes on with the clutch depressed. Sounds like you need three legs to do it all, but a stick to hold the gas pedal down does the trick. If you don't know how to shift gears without the clutch, you're out of luck on this trick.