Tom
Here's some pictures from my 34 rumble coupe (in storage)...let me know if they help. If not, I'll take more. Looks like the drain system is just the holes in the rear floor pan area?
My 33 trunk coupe has the (2) drain holes with tube mounts.
Shrunk the pics down for posting...but have them large..you can download these or I'll send the large versions to your email?
Ed