I tried everything above except the cold chisel... I would have done that, except the filter rides high on a protrusion in the tractor's frame. I would have had to have gotten behind it to give it a shot. Eventually, I managed to borrow a chain wrench with a two foot handle/lever arm. It took all my might and weight reefing on it to get it to budge, but it worked. The aluminum face of the filter was significantly gouged from the tractor frame, so the rumors of an 800lb gorilla at the Kubota plant may be accurate. The new filter was installed as tight as I could manage by hand... Somewhere between a half and 3/4 twist beyond finger tight. Thanks to all for the advice!