Don't know if the fitting on your dump valve is available. The dump valve fitting on our '65 Caravel
has been "out of print" for some time. Dump valve itself is available for ours, most likely for yours as well. You could check with Inland RV. They are knowledgeable, and have loads of parts. That's where I got my new dump valve.
You will need to remove the fitting from the valve to see exactly which valve you need. Someone had replaced the valve on our Caravel
and installed the wrong valve. It fit OK, but didn't have the "O" ring seal needed for the fitting, so they used gobs of silicone seal. It was a bit of a job getting it apart without damaging the fitting.