Reply to "Help wiring LED's. Im building/assembling a kasiners Passenger car kit from about 1949 and want to add LED's. But want to power it through the third rail."

You need a resistor and  you need DC not AC.   I think most 3 rail systems are AC but not sure.

I recommend starting with a 3000 OHM resistor (3k) and see how bright they are.   If too bright get highter - 10, if too dim go lower to 1.5k.     trial and error.  

For the DC, get a bridge rectifier.    Wire the leads from the track to the "AC" poles and wire the lead to LED to the + and - poles.    The long lead on the LED goes to the + pole on the bridge.   Trial and error here will hurt anything.    MAKE sure the resistor is next to the LED on either pole.

Radio shack used to sell all this stuff.    Now heed to find on line maybe - or All Electronhics