If Elton Brand played his rookie year in 1962, he would have put up Bellamy's numbers.
I agree with Bulls N Bears, players stats from that era are inflated. I don't know what it is, not everybody was interested in rebounding, but the numbers are ridiculous. In 1962 a 6'9 205 lbs Bob Pettit (according to BBref.) grabbed 18.7 boards. 205 lbs?
In 1961 a 6'5 Elgin Baylor averaged 19.8 rebounds per game. If a 6'5 guy can put up almost 20 boards per game, rebounding back then wasn't all that hard. My god, what would happen if Dwight Howard played back then?
I think a rookie Brand could average 20 boards in that era and if he got the shot attempts (23 for Bellamy vs. 16 for Brand) he could average the points. Bellamy is listed at 225 and Brand at 275 - although I don't think he was 275 coming out of college, but I'm not sure.
Some big men from that era could play today, but they would be average. A guy like Wilt would be an all-star. I don't think Russell would be because he was such a mediocre offensive player and he wouldn't put up crazy rebounding numbers like he did in the 60s, today.