Rust repair before paint, Passenger side longitudinal - 73 narrow body/4, now 6 conversion rebuild thread Options

[Montreal914]

Edit: I might as well make this my rebuild thread...

Original post; I got side tracked on my Microsquirt build as I have decided, after 11 years of ownership, to finally get my car painted to get her ready for her upcoming 50th birthday. (IMG:style_emoticons/default/smile.gif)
Knowing these endeavors can take a lot more time than initially planned, I hope to make it in time... (IMG:style_emoticons/default/wacko.gif) Well that date has long past now... (IMG:style_emoticons/default/rolleyes.gif)

Originally bahia red 73 1.7. The goal is a narrow body 2056 Microsquirt edit: stock 3.2 six, VW Tornado red edit: Adriatic blue, 5 lugs conversion with 15" or 16" Fuchs.
Front: 914-4 A arms with rubber bushings edit: Rebel Racing smooth bushings, 911 3" struts, Bilstein inserts, Alfa Brembo, vented rotor, stock torsion bar, 19mm sway bar, turbo tie rods, and 19mm master cylinder.
Rear: Drilled hubs, 914 PMB stock calipers edit: 914-6 calipers replica, 914-6 solid rear rotors, 140lbs springs, stock sway bar, rubber bushings.

But before I get the pleasure of installing all of these beautiful fresh goodies, I need to tackle the not so fun stuff... (IMG:style_emoticons/default/headbang.gif)

I have already started fixing some of the rust issues and will share that progress in the near future but right now, I wanted to post some of the issues i have on the passenger side front fender. (IMG:style_emoticons/default/sad.gif) I have searched and read many of the builds here but I would like some inputs from the people who have gone through this mess.

I am trying to understand the construction of the rear part of the fender, more precisely the area joining the front cowling.

Below is a sketch of how I think it is made but i would like someone to confirm...



Having removed the seam sealer in the upper rear area, I have discovered "this" (IMG:style_emoticons/default/dry.gif) which is not really unusual, but clearly a pain to fix. I am not sure though what I am looking at. If my sketch is correct, I guess the inner rusted layer is from the fender rear bulkhead that actually becomes an inner layer on the rear upper point of the fender by the door and cowling junction.





I might be able to cut this from the underside preventing me from cutting the outer surface of the fender. But I would like to better understand what is happening at the junction to the body.
How many layers are there from the fender, one or two?
Is the metal peeling off at the joint to the body the metal from the bulkhead/inner layer, or is it the outer fender layer?

As a reference, this if the situation of the channel, surface rust, but how bad? Is there a way to better know without destroying? Maybe poke with a screwdriver? (IMG:style_emoticons/default/confused24.gif)



Comments appreciated (IMG:style_emoticons/default/smile.gif)