If you dont have a Windy gun: Remove the clutch off the rear of the engine, you will see the flywheel bolts, now using a double ring spanner 14mm off the top of my head, place one end on a flywheel bolt and the other end on the one of the bottom studs. Im talking about the ones from the engine that go through the gearbox. That will lock the flywheel so you can crack the front pulley.
As Gordy has said you may need a puller to get it off, i use a small nylon mallet and tap it a bit then it comes off.
You may need to shock the clutch bolts off or even lock it off!