I didnt really answer the main question though -yes they are different - but only evolved, so a base model can easily be used to build a replica and use cosworth running gear.

The production 3dr cosworth shell was no stronger than a base model, I looked closely at both when building my cosworth as I had a base model run around at the same time, and all the sheet metal welds were the same

If I were building a replica or track 3dr I would start with a nice rot free base model shell and avoid the cosworth tax, but if I were reshelling a production cosworth I would use the cosworth version for resale value.