Areas that rust - Front panel lower
Lower Front Panel
Heres a video from 'Covkid' and 'Chickenkoop' showing another way of repairing this section using flat steel, bent at right angles in a vice, drilled and puddle welded to complete the repair. Spend time cleaning back to clean metal!
http://www.youtube.com/watch?v=LzA_xCEw0JQ
Its usually the front panel that rots where it meets box section behind bumper. Box section can corrode but usually all thats needed is a clean up of the front panel, cutting out the rot and welding in a bought or made lower section.
If you want to improve drainage in the area, drilll two or more holes into the horizontal section, just larger than a section of steel tube, taking these tubes through both layers so they exit at bottom, then making sure tubes are flush at top, weld them in. This will ensure any water which gathers has at least one or more routes out