I noticed that there is no gap between wing and the panel under the windscreen so yes there is heavy filler in this area, have you felt underneath this panel? I suspect you have heavy corrosion on the corner of the windscreen surround this is a typical area of corrosion especially on cars with sunroof (blocked sunroof drain tubes etc. ) with a sunroof it is important to keep the tubes clear, you are also likely to find corrosion at the front of the sill behind the front wing this is caused by water exiting the drain tube directly into the sill, a good modification is to pull the drain tube through a convenient hole that you will find at the front of the sill and passing it behind the plastic liner so that it drains directly onto the ground, it's a pity Lancia didn't do that!! If you are serious about renovating the car to the standard you have talked about I'm afraid there is probably no option but to remove the wing and investigate fully.
Yes there can be corrosion there, but I cannot see it yet, because it is repainted and first I must remove the paintig. It's a new information for me, that the sunroof has draintubes here, but I will check it, because I had also many problem with my Autobianchi A112 caused by closed drain tubes (f.e. this was caused by that:
http://blog.lanciak.hu/wp-content/uploads/2010/03/CB6.JPG )
The right front wing is already partially unset. My original plan was to restore everything in the engine bay in the first round, but I already can see that I must restore everything in one round in the front of the car if I want to do a nice job. I think that with unset front wings it is much easier to remove and respray the undercoating there.
