I need to remove the lock ring from the 240Z fuel tank, and I thought I would do a search to see if there is a tool to do that. Google sent me down several interesting rabbit holes in this quest.
I noticed that the lock ring for the older Mustangs looked pretty similar to the one for the 240Z. That ring was cheap, so I ordered one.
It is slightly larger than the 240Z ring. Many older GM cars/trucks have a very similar style and size, too.
The locking ring tools may work, but I didn't feel like ordering one.
Here are a couple I found:
http://blog.virginiaclassicmustang.com/2020/09/gas-tank-sending-unit-lock-ring-tool.html
https://www.ecklers.com/fuel-sending-unit-lock-ring-tool-25-255042-1.html
One of the other rabbit holes I explored was the Honda/Acura lock ring from the 90s. Once I found the Ford lock ring was too large, I thought that the Honda one might be closer due to metric system stuff.
I found the Dorman 579-015 on Amazon: https://www.amazon.com/dp/B002D3Y30U. At that price, I figured it was worth a look.
A new Z lock ring from ZCarDepot is on the left. The Honda lock ring seems to have the same inner and outer diameters as the Z lock ring. It only has 3 inner tabs as opposed to the 4 on the Z lock ring.
I plan on trying the lock ring on an old tank in the near future to verify fit. Given that the 240Z lock rings are cheaper, there isn't a need to switch, but we never know when supply will dry up.
As for a lock ring tool, I decided to make one myself.
A friend who has worked on a lot more Z cars than I have told me he made a similar one.