Did you do a search of the web? You can try Lincoln's web site and you can look in the AWS Handbooks or Kotecki's recent book (best source by far). I believe I also saw it in the latest edition of the D1.6 Structural Welding Code/Stainless Steel (I don't have it in front of me, its in the car and that's at my dad's house - I'm using his pickup truck - more than you wanted to know, huh?). The diagram in the D1.6 is the modified WRC diagram and it extends the Cr equiv. and Ni equiv. to include carbon steel.
As for the chemistry, the ASTM standards is a good strting point if you don't have actuals from an CMTR.
Best regards - Al