My floorboards are wet

[bad68bowtie]

I've been dealing with the cab leaking in various spots and I originally thought it was all because of the hole in the cowl where the antenna comes through not having a grommet or any other kind of sealent on it, but as I was working on it just now I'm not sure that's the only problem.

It rained here last night and as I went outside today to pull my truck in the garage to work on the leak a little more, I noticed there was a large amount of water spooled up on the dash just above the gauge panel. I suppose this is evidence that the windshield is leaking (frustrating because I had a new windshield installed not even a year ago) and when I turned the truck in the garage all the water ran over to the other side of the dash, and then all came out on the passenger side floorboard. After some investigating I found an indention in the dash where it meets the windshield and a slit cut in right below it. I thought with the indention there it looked like a factory thing and then I did find on the drivers side the same thing, only someone had packed it with silicone.

Are these slits something factory to take care of small windshield leaks? Also, what is the deal with the windshield? I've noticed some evidence of water before but never this much. I'm concerned that theres rust somewhere around the windshield but I'd like to think that when I had the new windshield put in the installer would've said somethin bout a rust problem. Any help and advisement y'all could provide would be great.