Yes. Nothing in the construction of Montblanc's rollerball refills has changed over the years apart from the thread. The refills available today can therefore be used in older rollerballs of the Slimline and Carrera lines, even though those models left the range long ago. In practice it is the only source, since refills from the period can no longer be had and would have dried out after so long in storage in any case.
With ballpoints the case is different: there the diameter of the refill tip was increased in the 1970s, so that bodies from the 1960s will no longer take today's large-capacity refill. Before looking for a replacement it should therefore be established whether one is dealing with a rollerball or a ballpoint; the two are often confused among the slim models of those years.