one thing leads to another
After calling every single auto parts store in town, I found out that nobody carries stainless steel fuel lines. So I bit the bullet and ordered a full set of pre-bent and pre-flared fuel lines from Inline Tube. Their web site is a bit hard to navigate, they don't have any sort of "shopping cart" for buying things, and they don't use a secure server, but hey. They set me back about $120 for the full set.

Just as I had expected, I scratched off some of the POR-15 when trying to get the tank back into the cab. I couldn't get it to fit with the driver's seat frame still in place (my truck has a "unison seat" for the driver that is separate from the bench seat), so I took the tank back out and went to work on the seat frame. I had been avoiding removing the seat since it was pretty thoroughly rusted in place, but as it turned out, all but two bolts were easily removed. The Dremel took care of those two, although I went through five of my roommate's cutoff wheels. With the seat frame out of the way, I test-fit the tank, and it went in much easier. I did notice that I'll have to wait for the fuel lines to arrive before installing the tank, as once it's in, it prevents installation of the line between the gas gauge sender and the flexible line that goes through the floor.

I tried to start on removing some of the paint and rust from part of the seat frame, but the paint was rather stubborn, even with Marine Clean, so I'll hold off on that until I get some more sandpaper. I put that away for later, and sprayed some Metal Prep on the parts of the gas tank that had been scraped clean of POR-15. I let that soak for about 20 minutes, then I sprayed water on it to clean it, and then dried it with paper towels and a hair dryer. I put one quick coat of POR-15 on the scraped-off spots, then cleaned up everything for the night.