AFAIK everybody considers the Ricardo boxes as quite good engineered, since they take HP figures of >1000hp without exploding. The short stillen final gear has been produced only in a small number (and I am not convinced they make fun in Europe since we can drive much faster compared to the US). I am not absolutely sure but I think the Ricardo Tranny was designed new from ground so there is nothing else that is compatible.
Since prices for cars and parts are rising, manufacturing parts for the tranny could be an excellent opportunity for someone who knows how to produce them.