Chuck says, "I have put many of your LEDs in HO scale, such as:
 
in Kato SD40's, SD45's, SD40-2's, C44-9w's;
 
in Atlas GP38's, GP40's, C420's, U23B's, C30-7's U33/36C's and C424/5's;
 
in Stewart C628's and C630's.
 
For example, every Atlas HO C30-7, U33/36C, and U23B engine I have now used your "W3" as replacement head and tail-lights.
 
I've used them in dummy Athearn HO models like SD45's and GP40's which I convert into liquid track-cleaners and place on the headend of trains to simultaneously clean the track and the diesel-engine wheels. I've used them as the light-source in tunnels and hidden staging-trackage to allow my electronic track-occupancy devices to read the light as track being empty, and then as being occupied when a train blocks the light.

Chuck's work has been appreciated & recognized by Columbia Model Train Examiner.
 

Chuck has graciously agreed to help with your questions relating to installation of our LEDs in Loco's. You may contact him at his email below. (The link is not clickable for security reasons.)