Airline maps asks "did Aeroflot not have an aircraft that could fly nonstop from Moscow to Vladivostok in the 1970s?." Because I'm that kind of nerd, I looked into it.
tl;dr: Only just barely.
The distance from Moscow (SVO) to Vladivostok (VVO) is just about 6425km (4,000mi). Russia's pride, the Tu-144 (aka "Concordski") could just barely make it: it's published range is also just about 6,425km. After that, the selection of airplanes which Aeroflot had that could make the non-stop flight was pretty small. Only the IL-62, with a range of 10,000km, could do it.
Surprisingly, Aeroflot's newest wide-body jet, the IL-86 couldn't make it (3,100mi range, which seems curiously short; that's barely trans-Atlantic range.) Nor could the workhorses, the Tu-154 or the Yak-42 make the flight non-stop.
On the other side of the Iron Curtain, by the mid-1970s, there were three airplanes that could consistently deliver: the then-still-Douglas DC-10-30 (1972, 10,600km range), the Lockheed L-1011 (1972, 7850km), and the Boeing 747 (1970, 8550km). Airbus was producing airplanes equivalent to the IL-86 at the time; not until 1985 and the A310-300 (9550km range) did Airbus make an airplane that could do SVO-VVO non-stop.
Note: This is published range. I don't know how winds, routing, and reserve requirements would have affected needed range (or if the Wikipedia figures have the reserve requirements built in.)