Water leak by kick panels

I agree that the cowl and vents are likely suspects but the adjustment holes behind the hinges are pretty big. The factory (at least on my '70) injected foaming sealer into the holes around the bolts. Without it there's a pretty good path for water and the holes are directly behind and above the kick panels. You can easily pull the kick panels, run some water over the area, and see whether it's coming in there or not.