Have you considered loosening the lug nuts, lifting Rawhide up and lowering Rawhide down? The force of the truck should be able to break the wheel loose, but the lug nuts partially on will prevent the wheel from flying off.
Also, have you used a sledgehammer with a longer handle? The leverage from the handle length may help. I had a similar problem with getting my spindle off my lower ball joint. I have a 3lb sledge with a short handle and was beating at it forever and couldn't get it loose. My Dad came by with a sledgehammer with a longer handle and took 2-3 whacks and it popped off.