I’d mod something else …NOT because this old light is so valuable but because it would be easier and the light is already way too large for no good reason . i’d buy a 2C rayovac or 2c eveready light that looks like the winchester … i like the C models as the fit better in your hand and will even take a 26650 if you want to use one instead of an 18650.
i personally don’t think you can make a real quality MOD without changing the light . i don;t think going back to stock is a real option …and the truth is …Who would ever really want to ?
I see the heatsink , the switch and the reflector as the main issues you may have to work out …the switch primarily why i say keeping it stock really just isn’t a viable option at all