The Stovebolt Site Forums The Parking Lot '60-'66 Trucks leaking above the windshield glass

If your rust is like every other 60 / 66 it is not a leak but trapped condensation in the top of the cab.
The earlier trucks had a fiberboard headliner that allowed the cabs to breath.

The ones like you have trap moisture from inside the cab , like from a damp floor. The moisture rises up into the top
of the cab because the area is open just behind the seat. but it has no way of breathing so the inside of the roof can be always damp.

The damp inside surfaces finally rot out the area above the windshield and will also rust the inside of the "A" posts. That is a lot of work to replace.

If the general had provided some venting possibly above and behind the sun visor, rust would not have taken away so many for scrap.
The floor and rocker panels are easy to replace compared to the A posts and windshield header.

It is a very nice looking truck. And 63 is the best of the early ones in my opinion. Nicest grill and badge treatment. First of the new suspension and engines.