ok, went ahead and crawled under the truck real quick because to be honest you got me curious. three out of four look to be in pretty good shape. the fourth one (passenger side front) looks like it got oversprayed with black paint or something. because all the other ones i can see the lights behind the lens, looks like LED's or something, and that fourth one looks just black. the housings have been painted white with the rest of the truck, and they attach with two bolts that go through the bumper and are fastened by nuts, and it looks like a power wire hooks to one of the bolts, and the housing grounds through the bumper into the chassis. when i take them off, ill check the resistance of all four of them, and see what i can tell you. Im not sure what the ohm spec is on these, but i would assume that somewhere between 0 and 100 ohms is ok, and an open circuit would be a bad unit. thats really the only way i can tell you if i think they are any good or not. unless someone on here knows a sure fire way to test them.
also, you might try asking around on steelsoldiers.com, bunch of military vehicle nuts over there. in fact, i think ill go post over there, and see if anyone can give me any specs on em.