E2d Mods

I ran across an old E2D in my kit this afternoon. The bulb is blown and i'm thinking about getting it up and running again.



I'd like to go with LED instead of the incandescent bulb that came with the light. I'm wondering though, what are the differences in using a Surefire replacement and a module such as this one



http://velenodesigns.com/html/surefi...d_drop-in.html



Also 123a batteries are getting spendy, I was thinking of a 18650 li-ion battery. Will it work in the E2D and what are the differences in brightness and run time when the 18650 is a 3.7 volt battery vs 6 volts from 2 123a batts?



Thanks for you input and advice



Berdar