DX review says it will fit a M@G w/a bit of work. What sort of battery power are you thinking? That driver has a 2.8 - 6V range so one Li-Ion or 3-4 NiMH cells will work.
The only problem with that drop in, is the diameter of the base. It's only 26.8mm and a maglite ID is about 34.2mm, so it will never touch the inside of the body. That means it would heat up fast and have nowhere to go. To fill in the extra 6.something mm, would take quite a lot of wrapping, with something.
I'm not saying no, I'm just saying look at the dimensions and measure what you got.