Look for .30 Carbine data for powder choices and to sanity-check the load data, but DO NOT just use .30 Carbine data in a .32-20 cuz it's too hot, and I can't tell you how much to back off.
2400 ought to be a good powder. And maybe AA4100 or W296 or Lil'gun, but those might be too slow or need higher pressure to burn right.
I remember reading an online article by Paco Kelly or Chuck Hawks or one of those guys years ago that had lots of .32-20 data of various power levels. Maybe I still have a link somewhere...
ETA: This might be it: http://www.leverguns.com/articles/paco/3220wcf.htm