Sweet car Rene – Thanks for posting!
I thought that in the mid 70s, the TVR corporation guaranteed their frames for five years from corrosion - to do this they would leave oil inside of the tubes before they welded them shut.
I do know the early Granturas had the fiberglass wrapped around the tubes at the factory - it was their build process. It was a huge nightmare to remove the body from the frame, to (first find, and then…) fix any corrosion.
I believe that starting with about the Vixen series, the cars were designed with a body bolted to the chassis, which significantly eased the workload of chassis repairs.
I can’t speak to Rene’s experience, but it seems like there is a benefit in trying to get those very few cars that lived in Southern California, or Arizona!
Rocky