I have an early 1935 trunk model coupe which didn't originally have any drainage system, however later model '35 & '36 trunk models apparently did. Picture below, which I saved from somewhere, shows the location of one of the corner drain pipes on a '35. The rubber hoses which take the water from there through the floorpan were part #48-725854 and are sold by several suppliers. Haven't had any experience with rumble seat models, but guessing they didn't have this system, as others have said, because there is not a "trough" across the bottom of the opening.
EDIT NOTE: Just noticed this is an OLD post and he's likely got it figured out by now!!