Ok, here are three of the easiest “biggest bang for the buck” changes you can make (my opinion).
Pull apart the pilot truck wheels and toss them! Using a rat-tail file ever so slightly enlarge the axle holes and install Bachmann small (24.5mm) wheels. You will need to “pull apart” the Bachmann wheels to install them…Then cut off the axle even with the hub.
(http://i273.photobucket.com/albums/jj222/Noble_Dreg/LSC/Atl1_zpsfe5cc186.jpg)
I also installed the same wheels on the tender. They are a tight fit, I found cutting a little off the ends of the axle made for a nice fit though you will want to de-burr the axle after the cut.
(http://i273.photobucket.com/albums/jj222/Noble_Dreg/LSC/Atl2_zps6619cd46.jpg)
I then used USA pick-ups screwed directly to the Lionel truck. I routed the wires through the fake ‘water-scoop’ actuator on the bottom of the tender. If you are very careful you can drill a hole through this casting and another through the tender floor and completely hide your wires.
(http://i273.photobucket.com/albums/jj222/Noble_Dreg/LSC/Atl3_zpscbe63684.jpg)
I also wired LGB lanterns on the tender deck replacing the jeweled markers.
That was it! My Atlantics will crawl or high-ball with the best of them! Some have added zip-ties to the motor and added weight, I have not done so and don’t really have a need. I don’t run long trains with these, 10 cars max. Probably make them even better.