If you want 2-rail, you can get a nice single motor power kit from P&D hobbies based on the original Weaver Drives. I suggest you ask for the Delrin trucks because they come with 8 wheel pickup. You have to design your own for the brass trucks.
Also P&D has a lot of various detail parts to customize the model including brass grab irons and lift rings which are much more sturdy than the styrene ones in the kit.