It uses a conventional thread (I *think* 9/16" fine), but not a conventional seal. Because the valve uses a banjo fitting, the sealing is done on the outside face of the valve body, not in a port chamfer like an ORB fitting, or in the threads like a pipe fitting.
The pic below shows an adapter you can buy that would allow you to connect a 3/8" NPT fitting to it if you'd like.
Edit: I just ran out and looked at my 6000 remote valve. It is indeed a 9/16" fine thread, and it does have a chamfer for an ORB fitting. I'm not sure that this is true with all similar-era Ford remote valves though.