I'm not sure that a new 5/16" sending unit is available for the 9 passenger tank. You may have to modify what you have to 3/8" or a repro if you find one

 

No new sending unit is available for that unicorn. I saw an NOS one on eBay sell for north of 350.00 about 6 months ago, they are so rare.
I did borrow the photos just for a reference. I saw it and 30 minutes later it was sold!

The larger fuel line size was only used on dual quad and FI engines. To find one of those in a 9 passenger wagon would have to be the rarest
of unicorns

 

Not any help at all, but there's an old man at the same "independent living facility" where my in-laws reside who told me his first job at GM was to design the gas tank for a 1958 Chevrolet station wagon. He's quite sharp for being 90+

 

Ok....Classic Industries has a new set up for the 9 passenger wagon in a 5/16th..... will go with that and see if I can modify it..... Made by Fargo Automotive...... so hard to find anything for the 9 passenger wagons.......

 

Expect problems

Expect problems. First will be the solder joint between the tube and the flat plate that mounts it to the tank. Then the ground is very poor quality and
will fail. Use the new one for a guide to refurbish your original. I speak from experience with FARGO junk.....

 

Have you tried Spectra Tanks

Fuel Tank - Spectra Premium

Each Spectra Premium fuel tank is factory leak-tested and made under OE specifications. Spectra Premium also has the most extensive fuel tank coverage

www.spectrapremium.com

 

shafers has what you need # GTS025 $80 813 628 0092 Larry chevyman57