Wow that shell corrosion/voids reminds me of my many old rear engined shells that I have repaired in the last 50 years mainly R8 and Dauphine, when panels were hard to find with no internet available in those days.
Lots of Gas welding was usually undertaken and wings cobbled together with non rusty patches , uk over cills were available and as these were removed everything is revealed and there is usually more rust in the chassis to deal with.
I spent a whole winter in the 1980s welding my R8 shell
chassis members from bumper to bumper on both sides, the wing tops and floors , after competing in the Coronation Rally on Epynt in 83 [second overall and my first rally], the shell felt soggy on the road and when jacking up it groaned around the door seals. After the repair it could be jacked up at any point without any groaning .
Previously to owning numerous R8 cars, I had Dauphines , and in 1976 I built a Proto with ex works Alpine A110 suspension and big
brake parts and an R17G 1605cc motor running on Weber DCOE carbs. The shell was a 1964 12volt but it succumbed to chassis failure behind the air intakes , at that time I did not know about the Queron built Dauphines in France with multiple steel tubing strengthening in the engine bay to stop the rear end of the chassis moving about.
I now have a 1958 Felec Dauphine project that I am on with this time I will add the Queron tubing as the Steve Swan Proto uses .
I intend to retire the R8 Gordini hill climb/sprint car and put it back to standard 1300G spec, then the big Sacco motor and 5 speed Wheeler box can then go into the much lighter and more aerodynamic Dauphine shell.
My R8 has alloy door skins which I fabricated, but the Dauphine doors are compound curved and may be a challenge to fabricate.
I see today that a French specialist offers 4 polyester doors, boot, bonnet and big wings to take the 7inch rims, Mk1 Escort big wings are close in design.
Cheers
Dave Wheeler