Seems like a good deal. https://phoenix.craigslist.org/wvl/pts/d/falcon-comet-ranchero-floor-pan/6768313571.html
That looks to be on the order of 22 or 24 gauge steel, quite a little thin for a floor pan, especially with a unibody car. Floors are typically 18 gauge, at least 20 gauge at the minimum. True - however, see the comment above about the material thickness.
Shame he doesn't have two of them. You could sammich them together like plywood and have a decent one.
Odds are, whatever the thickness of the steel, it's better than what you had. People are so picky. Me, I'd rather have solid floors that aren't as thick as stock, but look good, than swiss cheese floors.
There's this restaurant in San Antonio's called Schilo's. Ben there over 100 years. They have the most kick'n hot mustard I've ever had. I put some on my sandwich and with each bite felt the burn up behind my eyes, which were watering like a fountain. Epic. I brought home two jars.