how about with the task force series? (55-59) I looked inside mine and I think the back of the cab leaks at the rain gutter for perhaps water getting into the cab? It looks like the rain gutter is stamped into the shape of the sheet metal, so this might be a good time to just clear it off and bondoglass that bit to seal it (not like you could see it bondo'ed as the truck is so tall)

\'59 Chevy 1-ton
'72 c-10 (in progress)
The Great Rust(less) Mountain
\'47 Jeep cj2a