If it were me, I would not give up easy attempting to get those sleeves out. It is probably the rust on the inside of the sleeve that you are seeing. The rust on the outside of the sleeve may not be real bad.
Are there pistons rusted in the sleeve? If the pistons are out, I would do the obvious------ try a sleeve puller.
If there are pistons present and rusted in, I would consider two or three options. Option 1. With head and pan off, remove all four rod bearing caps from the crankshaft journals.
This allows turning the crankshaft to push up on ONLY TWO of the four pistons without consuming force to pull down on the other two pistons.
If the pistons happen to be near top and bottom dead center, turning the crankshaft, with rod caps off, has a great mechanical advantage to push upward and perhaps start moving two of the sleeves out of their bore. Whether successful or not, turn the crankshaft the other direction to try pushing the other two sleeves out of their bore.
Option 2. I am not sure there is a downside to carefully breaking the pistons out of the sleeves. Pounding too hard might break the upper shoulders of the block the sleeves are supported by. Whatever gets broken, it was mostly all junk before trying to break the pistons out. Itís hard to damage junk. LOL
If this block is still in the tractor and if the pistons are significantly away from dead center, there might be another option. With rod caps off, use a hyd jack and push up on one of the crank journals using a piece of wood between the crank journal and the jack. This can assist turning the crankshaft--- up to the point of lifting the front of the tractor off the ground. Clear as Mud? LOL