Stuart,
Why don't you or one of your group members contact BNSF directly and discuss it with them. They will then tell you exactly what they will and will not do. It is true that most roads don't like to accept friction bearing equipment, but may for a price. Also, they will expect the air brake equipment to be in date and functional. The main rods will also need to be taken down and the crossheads blocked in place. This will also mean that the running gear will now be out of balance, so it will have to move at a restricted speed. Just a few things to consider. If the locomotive has to be moved very far, the flat car option may be the best way to go. Good luck to you on this move and restoring the engine.