I was under the impression that "focal length" was a fixed design situation? Related to the distance between the emitting element and the mounting base? Which would require an internal design change to alter.
What bulb have you discovered which might be an adaptable replacement?
When the SuperLite was available, it was a neat deal, to me. In the mean time, might a set of good E-code lights be just as good, with their tighter beam pattern? Have you checked with Daniel Stern Lighting, as he appears to be a Mopar enthusiast?
Just curious,
CBODY67