It should go all the way to each side and drain out of a hole which you can't see unless the fenders are off. The water will drain down on the inside of the fenders just behind the front tire. This is what causes a lot of front fenders to rust out at the bottom.
I have pictures here: http://www.maverickcomet.com/TechArticles/TechArticles.asp The hardest part was drilling out the 100 or so spot welds. My car came with A/C, and the driver's side didn't have a hat, and that is where the rust hole was. Once that area was repaired with new metal welded in, I used several coats of POR-15 and seam sealer around the repaired area and weld through primer on the areas that would be welded back together. I knew once this thing was welded back together I wouldn't ever want to take it apart again. The cowl was welded back on with gas MIG welder and it is pretty hard to tell it was ever removed. Oh, and it doesn't leak any more