The EL500 uses an identical form factor LED to the dx one recommended. LEDs have increased in EFFICIENCY hugely since the EL500 was made. Meaning you get a lot more light out for the same heat production...ie the light will not get any hotter.
The led is mounted to an aluminium plate which is sufficent to dissipate the heat. The beam pattern is pretty much the same too, so the light pattern will be similar.
This is not the case at all for the powerbeam light, the optics are designed for a bulb not an LED, you will also have to find some significant sized bit of metal to mount the LED to, and build/buy and install a driver circuit (These are 6v bulbs I think, 4x AA batteries?).
For the EL500, you cut the front off, undo a few screws, unsolder the LED, check which way the connections go on the new LED, solder it in(thermal epoxy under the LED if you like) screw it all back together and glue the front back on.