These are things I have done to get them to come off.
Do as others say and get a good puller lined up straight and snugged up good and tight. Wack the puller straight on with a good heavy hammer. If you use a heavy hammer you don't have to swing it hard, but it will have a bunch of force behind it.
If that doesn't work, then take a torch, propane or gas just be careful because there are electrics behind the flywheel. Heat the fly wheel down by the crank shaft. Get it good and hot, so you can't really touch it with your had.
Check the tightness of the puller again. Now take an icecube and put it on the crank shaft end. You are trying to cool the crank shaft while the flywheel stays hot.
Another thing you can do is to do the above then take a brass drift and wack the face of the flywheel to shock it.
The final thing, if none of that works, is to put the puller on it good and tight and let it sit under tension for a day. Maybe even a couple of days. As it goes through warming and cooling cycles in the garage it will pop off.
I've always been able to get them off doing those things.
sled_guy