Any modifications needed to make a proper repair on this 66 cab?

[msg]

Looking for advice here, this area of my cab is needing repair and rather than start cutting and making it as close to original as I can...is there a better way to repair this so it dosent happen again? Looks like the gap may be intentional for the rain to channel from that spot in the windshield, didnt know if seam sealer is the best way to keep this from happening or if some other modification would be better.



A view inside, under the dash.