Interior Access Panel to Sending Unit in 70 Duster?

Sending unit lock ring wrench is your friend.

So how can you access the sending unit to replace it w/o taking out the tank? Sorry if I didn't mention I was replacing the sending unit...

After I get the tank out, I'm thinking about cutting my own access panel. Then cover it with sheet metal and a rubber seal. This is the fourth time I have had to access it only a few years apart! Where can I get a lock ring wrench? Thanks