after looking around a little bit it would seem like that light is the predicessor to the maglite. I see 2 things that make it stand out from a maglite in a modding perspective:
1) tube diamiter where you'd put a heat sink.
2) switch position/mechanism
1) if the tube diamiter is different from a maglite then you have to find a custom heatsink. (if it is the same then you cna order oen from some guy who makes mag heatsinks)
2) I'm not sure how that switch works but you may need to 'sacrifice' one of the D cell's space to put in some sort of spacer for the LED driver/heatsink.
so after that it sounds like a standard mag project.
my thoguhts on a mag project:
1) batteries (AA? D-cell? lithium?)
2) how much light do you need? exceptional light = $
3) run a build list by people here to make sure you arnt missing somehtign super important
4) order parts then build