FUEL TANK

[mattimuss]

I had the same issue when I pulled the tank from my Gramp's '41.  Here's what I did:
https://oldcarsrule.sdsu.edu/projects/matt/1941%20Plymouth/gas%20tank%20and%20trunk/first_start.html

[28 Ply.cpe]

I just went through this 3 days ago on a 49 P=18.  Took a couple days of soaking the nut /sleeve with penetrating oil. Mine did finally come loose, but I had the saws all ready to cut the straps. New straps and new sleeve nuts are available new.

[Lindsay McConnell]

The nuts you are turning are kind of sleeve nuts. They are long and the threaded end of the tank straps tighten up into them. Hit the threads with plenty of your favorite lube and carefully work those nuts back and fourth a few times. When you are ready to totally back them out, keep an eye on your straps to make certain they are not twisting. It does not take much to snap them off ! 

[Roachman]

I am trying to remove the fuel tank from my 1941 business coupe.  When trying to remove the nuts from the floor of the trunk that hold the straps into place I notice the straps are twisting too.  How do I safely remove straps without damaging them?   I also see what looks like a pop rivet holding the strap...