The Fulcrum is a Cold War aircraft. We can't simply judge the availability of information based on the era in which an aircraft served. For many governments and defense groups, classification doesn't have an expiration date. Meaning, there are aspects of aircraft out of service right now and have been out of service for decades that could still be classified simply because that paperwork is lost in an ocean of folders and filing cabinets. ED received a similar answer about the MiG-23 years ago. RAZBAM, however, is not subject to Russian law. That's the important part. The people running these organizations have one job and catering to us nerds is not part of it, sadly.
Realistically, all that can be done is inquire.