Will this fuel tank work?

Early A ('66 and earlier) had the bottom stamped for a single crosswise (frame to frame) support strap. They also utilized a smaller fill tube.
'67 and later used two longitudinal support straps, and were stamped for such. They also used a larger diameter fill tube, and as noted, various differences through the years for venting, emission and return lines.
Without seeing the bottom of the tank or knowing the fill tube diameter, I can't tell you which one you're looking at. I can tell you that it has an aftermarket sending unit with a return line, which is not a problem functionally- but it will most likely have some issues giving a correct tank level reading. The addition of a return line isn't a bad idea, especially with today's ethanol-heavy fuels; the only additions you'll need to make for it are adding the line itself, and a later (late '70s ish) fuel filter with 3 ports- it keeps cool fuel circulating and helps avoid vapor lock.
You'll also need to keep an eye on the sending unit lock ring and gasket. Aftermarket ones are notoriously thin and prone to leakage.