Caterpillar 12e clutch removal

Hi.
I have the engine out of my old Cat 12e grader. I am going to scrap it for parts. Part it out.
A guy with an old d6 wants the D333 engine.
I don't think he probably needs the bellhousing and clutch. Surely an old d6 dozer would use a different clutch and bellhousing?

I have removed the bolts around the clutch assembly. It seems the clutch wont budge loose from the flywheel?
Is there something I don't know? What do I have to do to get the clutch off so I can get the flywheel and...

Caterpillar 12e clutch removal