Steve, just curious why you need a new cap. Cracked, lost? Or something else?
I ask because I have seen 3 different iterations of the overflow system on these tractors. The setup I have vents the overflow out the threads of a solid cap. There are two slots in the male threads of the tank to vent it. My tank will spill antifreeze onto the injector pump until the level is at the LOW line. Now I leave it filled to the LOW line and all is well.
Don’t want you to spend money on a new cap if you don’t have to.