Stick a big pry bar in the exhaust ports and lift up on it. Do it on the front cylinder and then the back cylinder. That should unstick it from the block. Make sure you've got all the bolts out of the head first. I saw one a long time ago that somebody got crazy with and broke the head somehow.
A TEN tractor has a flat head engine. There are no ports in the head.
Cat 10, Are all the studs removed? If not there's probably rust around them in the holes. If you cant remove all of them you will have to pour some Kroil or other penetrating oil on them. You may try putting the nuts back on loose and carefully tap on them side to side with a hammer. Heat works too by sort of burning the rust out. Then just pry or tap where you can and the head will come off. Remember be PATIENT! You should be able to salvage the old head gasket if you don't get careless wedging a chisel or screw driver between the top deck and head,then you may damage the machined surface and will have to file or resurface them.
Thanks for the help!