In order to get Peyton Manning, I would give up any RB other than Tomlinson, Jackson, Gore, Parker, or Westbrook (in no particular order). If we're talking PPR, I'd add Bush to the list of RBs I'd prefer to Manning. I would also take Manning as high as 1.06 overall in an initial dynasty draft. To me, his value is comparable to that of Laurence Maroney.
I would not give up Carson Palmer and a top WR in order to get Peyton, but only because I don't think the gap between Palmer and Manning is that great. If I were to trade Palmer + a WR for Peyton Manning, I would trade any WR except for the following: Smiff, Chad Johnson, Holt, Wayne, Fitz, Walker, Evans, or Roy Williams.
Obviously, if you want to know what I'd be willing to trade Peyton Manning FOR, then just reverse the preceding statements. Anything that I would not be willing to trade AWAY to get Peyton is obviously something that I would be willing to trade Peyton away to get. Furthermore, it should go without saying, but all of this depends on league scoring and what my roster looks like- if I have Drew Brees as a backup, I'd probably trade Manning for Maroney. If I had Charlie Frye as a backup, I probably wouldn't even open discussions unless I was getting a solid QB in return.