The 2003 Red Sox set a new team slugging percentage record, breaking the long-standing mark of .489 set by the 1927 Yankees. Here is a look at the stats for both clubs:

           G    AB    H      1B   2B   3B   HR    BA   OBP   SLG  LG SLG

1927 NYY  155  5347  1644  1092  291  103  158  .307  .381  .489   .390

2003 BRS  162  5769  1667  1018  371   40  238  .289  .360  .491   .420

The last column is the league slugging percentage, minus the teams in question. While Boston has a higher slugging percentage, New York's was higher than the rest of the league by .099; the Red Sox were .071 higher than the average of its peers. The Yankees slugging was 125% of the AL average, Boston was 117% higher. If my math is correct (and tell me if it isn't), the Murderers Row mark is still the best, when put into context.