Thanks for all the input.  My EM-1 is 7627.  I found photos of 7627 before and after it was renumbered.  No evidence that it ever had the twin sealed beam headlight.  My model came with that one installed.  The other headlight came in a package with two leads not attached to the light.

The EM-1 comes with an alternate headlight.  I would like to install it in place of the factory installed one.   Anyone have a suggestion about how to change the headlight?  The locomotive diagram says nothing about this.