This is a very old topic but I'm adding some info that might help others even service techs. Also, have a trained propane professional do any propane related work.
First: This site has great photos of the Auto Stop valve:
The Infamous Auto Stop Propane Fill Valve. | arts-attic.com - A copy of the patent is also on that site.
Next: The body of the Auto Stop valve separates from the hex (nut/bolt) fitting. The hex fitting is a bushing with very fine threads on the hex to Auto Stop side and NPT threads on the hex to tank part. This means that you can remove the Auto Stop valve body to gain access to the hex fitting.
I discovered that by accident. I couldn't access the hex nut fitting so I used a plumbers slip nut wrench to rotate the Auto Stop valve body. The fine thread fooled me into thinking that it was swivel type coupling as it didn't seem come away from the hex nut. Rotating the Auto Stop valve body a bit did permit some access to the hex fitting but I soon got stymied there. So I went back to the Auto Stop valve body and discovered that it was coming away from the hex fitting as I rotated it. Once the Auto Stop valve body was removed then it was easy to remove the hex fitting.
The new valve was installed in less than a minute as I had a 1-3/4" socket ready to go. The new bleeder valve was also easy to install.
I have a combination of fittings that allows me to transfer some liquid propane from a BBQ tank to the approximate 40lb ASME tank on the van. The transfer was pretty quick and the tank gauge moved to 15% confirming the transfer as well as the new unused Exchange type BBQ tank had reduced to 1/4 full. (Exchange tanks have 15 to 16 lbs of propane from what I've read)
Note that the new fill valve is not an OPD type. This means that the bleeder or spit valve has to be open to know when the tank is at 80% full. Always make sure that the filling attendant opens that bleeder valve. From what I've read on the internet, it seems that there is no federal or national requirement that
ASME tanks have an OPD fill. Some states do mandate that though so do your research.
DOT cylinders must have an OPD fill valve.
I don't think that an OPD fill valve is available for the tank on my van as the fill inlet looks to be at the 50% level so considerably lower than the bleeder valve. Newer tanks appear to have the fill & bleeder at the same level (80%).
In my experience, filling attendants always open the bleeder valve anyway but I have read that sometimes they don't. I'll just make sure that the filling attendant opens that bleeder valve.
Note: Any work on the propane system should be done by trained professionals.