67 Fastback rear deck filler panel repair ?s

67 fastback, some po installed 68 stainless trim and 'fixed' the rear panel below the glass.

Water will sit at bottom of rear glass and not leak into cabin.
When raining, whether driving or stopped, minimal water gets in trunk on both sides.
Trunk is completely solid, not even surface rust.

Looking from inside out, not so easy to do, the one hole to the outside is visible but I don't see any other rust.
Not easy to see and impossible to get a pic.

Driven all the time, never an issue, never got worse, at this point I just want to fix correctly. I haven't had any luck finding good pics or any other fastbacks with this same issue.

Can the rear glass gasket be reused, best guess?

Wtf is this rear panel supposed to look like, leaded seam, something else?

And where exactly is the seam supposed to be?

Any education or pics before I tear into this is greatly appreciated.

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