Chess History: The Number 1 vs The Number 2

Hoping you guys can help me out.  I am looking for info that compares the number 1 vs number 2 players throughout history at various dates.  Mostly I am interested in ratings. So for example March 2016: Carlsen has a live rating of 2851 vs Kramnik  at 2801.  I plan on doing some of comparison then putting together an article but I am having trouble finding the info.  I didn't think it would be this hard!

Any info you guys can dig up throughout history is appreciated...even if it is something you just remember off hand that I can research myself later.  Also any links or websites showing this info would be much appreciated.  Even old cached pages.  Thank you guys/gals for your help in this.