I tried various LED bulbs in the passenger cars for years. The LED bulbs just weren't bright enough out the side, but mine were 2 bulb cars. Running TMCC at 18v, some burned out. Many are designed for 12v. The best I got with the bulbs was to glue a small sheet of white translucent plastice on top of the bulb to diffuse the light to the side.
Try one car and compare with the incandescent and see if you like it.
I now use a voltage adapter and LED strips glued to the roof when I convert a passenger car to LEDs.