Clearance marker lights, the joint between the front cap and the roof/sidewalls, etc. Sounds like you have narrowed it in already but you might want to try the "hose test".
Get up on a ladder with a garden hose on low. Have someone inside the coach looking for water coming through the known leak. Move the hose to different places that could be leaking in the general area. Depending on the speed of the leak you may want to wait 15 - 30 minutes between tests and it could take a while for the water to reach the inside.
You may be surprised where it's coming from.
1986 Airstream 345 Classic Motorhome