Well, you can add me to the list of puddled up floorboards. Yesterday we had our first big rain of the season, I didn't drive the truck yesterday cause I've got to replace my clutch master. When I got home last night I went to pull it in the garage to replace the master and to check for leaks. Luckily there was only one puddle on the drivers side and tracing it down it looks like the same spot as you. Took the fender off and she's pretty clean under there, the truck was wrecked and repaired before I bought it so I figured just shotty repair welds. At least no rust, so I'll be cleaning the seam out really well and applying a generous amount of POR15 to the seam this weekend. and crossing my fingers.