Will a 1999 single cab ranger box fit my 2003 edge ex cab? Both boxes are 6 feet... Also will my 03 tail lights fit in the 99 box? And will the gas fill neck line up? If anyone has anything on this info please let me know.

 

Easy thing out of the way. 93-11 tail lights will ALL bolt up to each other, regardless of year. 1993 all the way 2011. However, in 2000 they swapped from a three bulb to two bulb system. In 2000, the brake light and turn signal are now combined. 1999 and earlier years had separate turn signals. However, in this case, this matters not since it appears you're wanting to reuse what you already have.

In short, yes the lights will bolt on.

Now, beds. There's no reason why they shouldn't fit. The ranger was largely unchanged between 98-11. Here's the major body panels that changed.
Front end changed in 01. This includes headlights, grille, and bumpers.
Hood changed in 2004.
The step side bed was no longer offered in 05.
That's pretty much it.

The difference between flair and style side may make a difference, but I doubt it. Like I said, the ranger (cosmetically) underwent few changes. That being said, the filler neck should also bolt up with little issue.

 

Later in the Ranger lineup, around 2008, Ford added one more row of bolts to the bed. But this makes no difference since you're trying to use a 1999 bed on a 2003. You'll be just fine.