Gotta disagree with MMII. The 2008 edition of API-537 and ISO 25457 have been 'normed'. They are now identical, thus it is reasonable to expect that there were some changes between the 2003 edition of -537 and the 2008 'normed' edition.
It is also reasonable to expect that -537 looks a lot like it did in the 2003 edition. You're going to have to buy a 2008 and look at the revision history. A 'plain' API-537 2008 costs $210 and a 'redlined' one [showing all the changes and reworking] costs $263.