My 445 just started to over heat, so I began to diagnosis-ed the cause, i.e. radiator screen, side panels, etc. I'm leaning now towards the thermostat or the radiator needing flushed. I went to check the price on the thermostat in JD Parts. The kit, which includes the gasket, is part number AM121668. It turns out it's obsolete and to check the dealer. Talking to the parts guy at my local dealer reveals that Deere separated the thermostat and the gasket. The thermostat is now $30.38 (the old kit was over $53). So, if any 425 or 445 owner needing a thermostat, they are still available - you just need to contact your dealer.