Converting 320 for oil drain valve

[dilligaf241]

I am trying to get the size oil change valve I need for my JD 320. It has the FD590V engine. I just put in full synthetic and really don't want to drain it back out. I backed it out a few turns and put my micrometer on it and it came in at 18.5MM but I couldn't get the thread part. Not even sure that the 18.5 is accurate because of the limited space. Any help would be greatly appreciated!

 

[Teddy1973]

Since nobody else has suggested after 5 days, I will, have you asked your local JD dealer? I would think they could find out pretty quick for you.