Alright, let's see
Fetisov - Kasatonov
Vasiliev - Pervukhin
Lutchenko - Thygankov
Konstantinov
You think ANY defense in hockey history would have edge in defensive play before these guys? I highly doubt. The only player who could change something would be Orr in his prime. But as far as I remember he never played for Montreal.
Maybe I should have said 'defensive depth', but here goes...
The Soviet defense in the 1970s SUCKED (except in 1978-79). That's right. Look at the 1972 Summit Series, for example; Team Canada won it on grit and
better defense (and by taking out USSR's best forward, but let's not get into that now); even guys like Gary Bergman and Bill White were better and more reliable than the best Soviet d-men in the Series. Vasiliev was certainly better than either of them in the long run, but he was young in 1972.
Fetisov and Kasatonov were brilliant, as was Vasiliev. After that, a huge drop. So yes, IMO defensively Montreal's dream team would be at least as good on top and would have clearly more depth below.
Edit:
Forgot about Ragulin; he wasn't in his prime anymore in 1972. He was certainly as strong as they come, but still a slight question mark. Guys like Sologubov and Davydov are also big "what ifs"...