Not an expert! But, I don't buy the explanation of the tank's construction has anything to do with the fuel gauge. He's probably right about it being a replacement as finding an original after 70 years still in usable condition would be unique.
The gauge reading can be affected by fuel slosh but not pressure. The baffle helps with sloshing but must have enough openings so as not to restrict flow. That sloshing won't create a non-stop permanent inaccurate reading. It will fluctuate above and below as the "waves" bounce around inside the tank. Sit still for a traffic light (or similar) and you'll get enough settling to read fairly accurate.
A word of caution on reinforcing: You may not like the way the tank looks after it's been reinforced.
I bought a grey replacement from Walck's a few years back and really liked its construction. I ruined it by having a shop line it (incorrectly thinking I'd turn it into a "lasts forever" tank. After several unsuccessful acid baths, a different shop cut it open and blasted the liner out. The liner didn't line the tank, it puddled in all the wrong places. The resulting patch to seal the tank back up looked really bad. It would've been functional but the seat wouldn't have been able to cover it up.
I bought another tank from Pet Debella,
http://www.debellajeepparts.com/cjpremiers.htm, and am very pleased with it. For it to fit correctly in my jeep, I had to remove the square bracket on the back - and of course that created the need to repaint. But it fits (minor adjustment to the floor openings) and works.
I used the method of adjusting the sending unit that Dr. Vern illustrated on his website (before he took it down) and was able to get full range on the gauge. I then altered the arm (without cutting) to get full at the top and empty at the bottom. All of this was done outside the tank where you can observe and adjust the float.
