I made a few bulb replacements on my Discovery. The stock turn, reverse, third brake, and rear fog lights are 1156 or P21/5 (both are printed on the fixtures). Those bulbs are nearly identical and they match the 32CP (candlepower) specification also printed on the fixtures.

I found that LED replacements for the "1156" style bulb socket do not even approach 32CP or the roughly 400 lumens the stock incandescent bulbs produce. LED replacements will be much dimmer. In some cases this may be ok. I'm using them in my brake/tail lights (1157 style) and turn signals (1156 style).

But if you want bright, then there are three choices I've found. The brightest is perhaps the 50W 1156H (Halogen) from Eiko. These very well may melt your housings and will probably not wow you with brightness compared to a complete lamp housing from Hella, Rigid, etc. But you can have significantly brighter light without more heat.

The 3497 bulb fits the 1156 style socket and provides 45CP or 566 initial lumens with the same 25W power consumption as an 1156 (32CP and 402 lumens). I compared them to the Sylvania Silverstar 1156 which sort of claims 40% more brightness (they won't actually make the claim in words but use little diagrams to try to tell you what they're claiming without actually making a false statement). With my eyes I could see that both the 3497 and the Silverstar were much brighter than a standard 1156. I could not tell whether the Silverstar or the 3497 was brighter but the Silverstar had a higher color temperature possibly due to the neodyium coating which filters (reduces) some longer wavelength light.

I would put the Silverstars in the clear reverse housings, and the 3497's in low color temperature housings (red or amber). The 3497's are significantly less costly than the Silverstars. I use them in the rear fog lights and the third brake light (where window tint really kills the LED's).

You can also get 3496's which are the dual-filament version for brake/tail lights. I have not compared them to Silverstar 1157's but I imagine the comparison would be similar.

The Discovery 1 also has a number of sockets for 194 style bulbs. Some of these are eliminated with aftermarket bumpers. Others can be replaced with SMD's.

There's also a number of 37mm festoon bulbs in the dome lights and license plate lights. SMD arrays work nicely to replace the festoons which are easily damaged by vibration.

 

In my experience LEDs just don't last in any kind of external light housing.
I'm back to using regular old stock bulbs for everything else, including headlights. I got tired of dropping $50 on the SilverStars every time one burned out. They were nice and bright and white though. Between the Hi beams and my two Hella 4K's I've got more than enough light.

 

LED's in a tail lamp are a very very bad idea, they dont disperse the light in a nice wide pattern, you cant be seen from the sides.

 

Good god man, you know your bulbs.

 

LEDs for interior are a big plus, more light, less amps, and the multifunction unit won't burn up so quick.

 

I replaced all interior bulbs with the LED what a big difference I can actually see what I dropped on the floor.

 

I put two red LED's in the REAR sidemarkers.
Amber in the front side markers.
Those were burned out for --years???

Simply LOVE it.

4 LED's are ganged up and pointing right out of that lens.

Now maybe people will see the truck from the side..
Was dark before.