Interior Access Panel to Sending Unit in 70 Duster?

Mega Parts has the wrench, it's under Air/ Fuel, then look for hardware and tools, towards bottom of page. $15. They are in Wisconsin.
Do you have a new tank or an original?
The lock ring area in my old tank (and it was pretty new when I bought the car) was all stretched out of shape. I got a stainless steel tank after that, it too started to leak, not sure why. I just Pro Sealed it together 2 days ago. ( Aircraft tank sealer) it wont leak again. Someone makes a 2 part sealer for fuel like that, maybe google it.