My '94 Ranger super cab gas tank did the same thing- a hairline crack, or split, all by itself, on the upper front of the tank. I repaired mine with regular 5-minute epoxy, and two years later it's still holding fine.
If you're going to try and repair yours, brew92, I think the most important thing is prepping the area before you apply the epoxy or plastic weld. I drilled tiny holes at the ends and along the crack, and then roughed up both sides with 60 grit sandpaper. Drop the tank, pull the fuel pump and work the inside through the hole. Then just clean it out real good before reinstalling (use a big towel inside during the surface prep, too, to catch the dust when sanding).