Go with Nightforce, I prefer the SL170, they also make an SL240, but it has the same candlepower, only a largers reflective face.
It wieghs next to nothing, and is the only light I have ever used that seems to put out as much light as it is publicized to. 1,000,000candlepower.
I have a 2,000,000 candlepower light that puts out about half as much light.
You can get a battery pack with a diode for dimming, and the light can be plkugged into it with the same cigar lighter plug as you would use from your car. If you don't want to use a cigar plug in the car, you can spaw to alligator clamps, all this is without having to cut the wires, there are little plugs on them.
You can buy an attatchment to put it on the roof of you truck, either via a hole drilled through it or a suction cup version, as well as scope mounts for it, (the SL140 is best for this)
They also have a seres of different colored covers and filters.
We do a lot of spotlighting in Australia and they are very popular.
www.nightforce.com