King Glamis,
LEDs are ready, when teamed with the right optic/reflector. You will need a tight beam for the best throw. The nice thing about LEDs is you can get just about any brightness of light just by toying with the number of emitters+reflectors, and the current. You can exceed the brightness of the standard 50W halogen in lumens with 10 LEDs, or step it up 16 and rival the standard automotive HID lights. Of course, this is using the easy to attain Cree XR-E P4-bin or Seoul P4 U-bin. Price comes to mind as being slightly troublesome if producing very small numbers of off-road lighting units (ordering from a reseller), but if you have to order in bulk right from a distributor, you will save a bunch. You can talk with Fraen, Polymer Optics, or Carlico Optics (or any other optics company) and have custom reflectors made for these. If you do not want to go custom, there is plenty of low-priced reflectors and optics for you. If you go with Seoul P4 LEDs, you can use the standard IMS27XA reflectors found at Future electronics (they cost about $1.73 each). They have a tightly focused beam that may work for you. As for Cree XR-Es, they are a little harder to find cheap reflectors for. There are plenty of optics that will fit them, and the beam produced is not that bad (for throw).
This just depends on how much money you want to make these for, and the final size of the enclosure. All of this is viable, but you just have to consider all the different factors, I suppose. I have made 2 headlight clusters using 18 LEDs each (K2s when they were not that bad), and they use Fraen's 27mm narrow FHS optic. The beam is pretty tight, and each cluster is pretty dang bright. I estimated that it puts out 1800lm at about 40,000lux. That is conservative, too. With Seouls, you can get that with just half of the emitters (the cluster would be half the size). If you use 18 Seouls, then expect twice this brightness!
I think that some will say discouraging stuff about LEDs because they compare their smaller hand-held LED flashlights with their brighter (and sometimes bigger) incandescent versions. Or, they will compare it with their car's headlights. I agree that single LEDs will never cut it anytime soon (even Osram's future "1000" lumen LED). However, once you start adding up the emitters in the cluster, the brightness starts to get extreme and they will compete with your big incandescent and HID lights.
HID is tough to beat because of the small light-emitting point and big single reflector, but do not let that get you down. You can drive higher speeds even with that super-tight beam of light. Oh, and that super-blue tint from those LEDs in the previous pictures is a big problem, but only for that manufacturer. You can easily get warmer tints that are warmer than HID (which is still pretty blue). Color rendition will be good and it will make you feel better when driving down the dirt roads. I suspect that the manufacturer of that light bar did not understand the concept of tint when he ordered those LEDs. In the eyes of us CPF'ers, you can say that they got screwed! You can do better than that. Like mentioned before, they did use some low-efficiency LEDs in that light. I seen that light bar before and discussed them. You can do better! As for light scatter, that should not be too big of a deal. With the cool (but not blue) tints, expect the same scatter as HID. A too wide of a beam can cause a distraction problem, though. If it is foggy or there is dust in the air, then you should have fog lights on your truck! You don't drive in foggy conditions with driving lights on anyways! I don't do so with my high-beams on.
-Tony
