regarding athleticism, TWO high school runners broke 4 minutes in the mile for the USA in the 1960's and it was around FOURTY YEARS before anyone did it again. Mantle was hitting 550 foot shots, Bob Feller was throwing over 102 mph, William Russell was barely trying and jumping 6'9" in the highs jump in HS, and Jim Brown, at his size and speed, was the best running back in the NFL and maybe ever. The marathon WR was 2:08 and change and that held for 30 years. We can talk about the long jump if you want.
Cowens, Nelson, Silas, Havlicek, White, Chaney, Westphal vs Perk, KG, Pierce, Ray, Rondo, Powe, Posey, House? IMHO and all in fun: Cowens would have had to handled KG, Silas would have dealt with Perk, Havlicek vs PP, while Chaney would have been glued to Ray and white would have just destroyed Rajon. They really would have killed them. They match up even better than the 80's Celtics would have, imho