I'm in a 12 team keeper league. Each team get to keep 6 players. My keepers as of now are:

Gannon
McNair
A. Green
E. James
Dillon
Moulds


I may be able to trade one of my running backs for either Harrison or Moss.

Do you think I should pursue this trade? And what running back would you trade?

Try and keep your backs and trade one of your QB's for WR help. You certainly won't be able to get a Harrison or Moss type, but if you find someone with a weak enough QB, then try and work a deal for them, considering you will only be able to play one of your QB's. If you have to trade a RB, trade Green, as he's the most injury prone.

I think I could get Jimmy Smith for McNair...

The wheels are coming off Jimmy Smith....try for a lesser known #1 guy like Todd Pinkston or Donald Driver....or a #2 that may be the next Peerless Price. Porter in Oakland comes to mind...and would be a fantastic keeper pickup.