Help with swapping engine on my 30" rear engine Snapper

I have a 20 year old Snapper mower. I'm replacing the old ( it is locked up) 10HP B&S with a new 10HP B&S. The problem is that I can't get the disc/pulley assembly off the old crankshaft. This is the one piece design. I have removed the 2 allen screws, applied Liquid Wrench, and I have heated the assembly....It will not budge. I have tried whacking it with a hammer just to break it free. Nothing moves it. Are the 2 screws that hold it to the crank the only means, or is the 1 piece also threaded to the crank. Before I order a new assembly, I would like to save this one. You can call me or post. Matt @ 404-641-4273