This required no modification at all. I bought this '60s Eveready Captain 2D on eBay for $5. Took the bulb out and suspected that one of my lame leftover 3 watt LEDs meant for a Mag-Lite was the same size. Sure enough, it dropped right in and turned this almost useless vintage incan into a classic chrome can, with some modern umph.
Kinda fun, I guess.
sentinmentalFoy
Shiny! 
Put it back on ebay as an archeological wonder! State that the light is stock and very old. Maybe came from Atlantis they invented high power leds centuries ago...
If you can pull this off all you make out of it is truly deserved.
ebaysuckerfinderFoy
Nice , .... I have a 3D Tin wonder from the 70's [ My first flashlight ]
I took a bulb , riped out the guts , and planted a SSC P4 emitter in it , making it LED , not a very good beam . but a trick mod ...
Now it runs depleted D cells , and puts out decent light ..
Fully or partially charged cells make it run too hot [ ?? to 4.5v ] since the little bulb is all there is for heatsinking . But the depleted cells are just right , going on 2 years now with some old depleted cells and still works great .
Yeah, the beam pattern sucks on this one too. It was just a slight eyebrow raiser to simply drop in the LED, power up the old girl and see it put out 5 times as much light as it did.
chromecan/incanFoy
Just picked one of these up 3D, was £10 I’m going to convert to led to, not sure wheather just to get the drop in or do somthing a bit more extreme…. 
go extreme would be my take on it. :sunglasses:
Damn, seen a thread with foy as the thread starter, couldn’t click it fast enough. Now I’m sad.
Anyone know where I could find a spare reflector and lense for one of these???