Hi Jason
Interesting subject and there is not a lot of info around. The main reason was that the Stratos was homologated for rallying at the same time as the Beta Coupe, the Beta was very much the poor relation and from what I have read only ran for approx 1 year (maybe 2?) in Intl events as part of the factory team.
I have a copy (maybe not complete) of the homologation papers if that helps, but depending on how strict they are, it will be a difficult one to replicate. The reason being that the G4 car ran a special Abarth 16V head as well as the twin IDF carbs, with the engine inclined even further than normal. The G3 car, I am unsure of as the G4 and G3 descriptions in everything I have read get merged, so suspect the G3 had only a single carb as per production. No idea if the car went circuit racing Internationally, just the records of the rally versions appear online/in print.
Peter