I’ve been tolerant of a very minor auto trans leak for a long time. It was from the fill tube nut and flange. I had to used the original 56 even on the 62 C-O-M I had installed and the very minor leak was still there. I needed to put the car up in the air to change a failed oil light sender and check the oil pressure relief so while it was up I decided to install the new tube and dipstick I bought from Larry’s T-Bird parts while ago. I might have been taking a chance because no mention was made to any year passenger car. The tube fit fine and the leak is gone.
I could never see anything wrong with the old mating surfaces but something was there and no matter how tight I tried it leaked. Glad that’s done.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I used quality Pipe Sealant Tape and coated it with Permatex Aircraft Sealant. No more Leaks.

  

Tried Teflon tap and permatex sealant and it would work for a while then slowly drip again. Trans oil can follow the threads as the threads are not the sealing surface. The taper on the tube and the fitting machined in the welded nut on the pan is. If l could have found a soft copper washer without making one I would have tried that. Not long ago I found that a new tube was available and Larry’s sold them so I drove over an picked one up and this was the first opportunity to change it. Thanks anyway and glad it worked for you..

56 Vic, B'Ville 200 MPH Club Member, So Cal.

The Flare  end of your Tube must have been worse than Mine. I thought about using an O- ring or Copper Washer also but luckily Tape and Sealant worked. I knew that new Dipsticks were available. Didn't know the Tube was also. Good to know.