I have the Rio Grande service station set from the 70's. I replaced the power truck with a postwar power truck, and replaced the armature with a postwar one, Now the engine (although single motored) has magnatraction and runs extremely well. I paid a third of the price of a postwar F3 for the set!
I have also done the same thing with an MPC Virginian rectifier, I now have a great running engine for much less than the post war version. You may want to try this out, a lot of MPC especially from the early 70's is left over stock from postwar lionel.
