I'm curious if there is anyway to easily put a decoder in an old time 4-4-0. Any suggestions?
There are various values of easy.
Put a DZ125 decoder in the tender with the motor. Use you imagination for location.
Follow the instructions that come with the decoder.
Rich
I did the below about ten years ago using a Lenz N scale decoder.
(http://i98.photobucket.com/albums/l267/richg1998/4-4-0mods.jpg)
You will need Harold's idea for better pickup.
http://www.pacificcoastairlinerr.com/bachmann_4-4-0/wipers/
I doubt a Cave Man could do this but you probably have the skills or can develop them. That is what I have done over the years.
Rich