Hey Vic.
Yes, Dodge does offer the cab lights as an option in the 2500/3500 SRW trucks. My truck came with them as standard, my dealer told me it was because it was a 1-ton. All the 3500's on their lot had them. I also noticed all the 3500's on other lots had them too. Since I was looking for a 3500 I did not pay attention to the 2500's.
The cab clearance lights go back a long time ago and were required on semi trucks because they pulled an 8' wide trailer and their width was also 8'. I cannot remember what the exact number is, but the law says that vehicles and trailers with over x# amount of inches wide have to have the cab clearance lights and the rear markers. It does not make any difference whether you are private or commercial use, it is about the width dimension of the vehicle and what it tows in width dimension and lighting reqs based on width dimension.
When that law was written, I do not think that too many privately owned, non-commercial vehicles were as wide, and I don't think that there were many trailers being pulled by privately owned, non-commercial vehicles. Then along came the RV and Dually explosion, more and more of the heavier big-block and diesel trucks hit the road, along with larger trailers, etc. All the trailers were lighted according to the DOT, but, the trucks were not. Some mfr's offered cab lights, some put them on, and before long we had quite the mix going down the road. Since the homeland security stuff, the gov has been more and more calling for vehicles to meet the DOT regarding lighting.
It really could mean that all those who added the cab lights MUST also add the gang-3 rear center markers regardless of their size and weight class, because of the lighting req's for both ends of the vehicle. As far as the DOT Laws, yes, they are illegal. As far as the homeland security laws, yes they are illegal. The law states that the cab lights and the gang-3 markers must both be there, have one-must have the other. If you just have the cab lights, you will soon be reminded about the others. I had a friend who put a set of the gang-3 rear markers on his truck, mounted them on a piece of angle just below his hitch. He thought the additional lighting in the back was a good safety feature. He got a ticket for not having the cab clearance lights. This was a couple months ago. His truck is a Ford F-250 2x with a 460 gas engine. He was stopped by a state trooper in TX for a minor moving violation, the trooper gave him a warning for the moving violation and ticketed him for the lights. He removed the gang-3, returned the lighting to stock, and paid his fine. Then a few days later he was pulling his flatbed gooseneck and got waived into one of those roadside checks. His flatbed IS 8' wide, and he got a ticket for not having the proper lighting for pulling 8' wide trailer. Now he has his gang-3 back on and installed the cab lights. All of this cost him some big bucks too. He is not commercial, has no signs on his truck that would indicate otherwise, all private use trailers, etc. The funny part about all of his stuff is that I have been telling him for some time that he needed to get his lighting in order and he kept telling me that he was not commercial and I was full of it. What was even better is that the state trooper told him he was lucky he was not driving a 4x4, then he would have also gotten a ticket for having more than 3 axles in combination because the 4x4 has 2 axles and the trailer has 2 axles. A general non-commercial drivers license is issued for 3 axles in combination and has a gross combined weight value. They did weigh his trailer and he just barely was under the gross combined weight or he would have gotten a ticket for that too. My friend was really flustered by all this stuff, and so will everyone else when it happens to them too.
Soon, all states will be like CA and have the additional drivers license endorsements for the way we use our trucks too. Towing trailers over a certain weight and length, etc. Again, this all will fall under some of the homeland security laws, and the DOT will add them over time. The objective is to make all states have the same laws, standardize this stuff across the board. The fed DOT can and will enforce these laws on any/all roads that they contribute funds to the construction and maintenance, and any roads that interconnect states.
The truck manufacturers have been served up all the compliance notices, we will begin to see all the vehicles getting the lighting in order out of the factories and off the sales lots, and recalls like Dodge did this past summer to get everyone straightened out. I'm expecting that any day Dodge will recall for the gang-3 req for the back of my truck since the cab lights came standard. Then, once everyone has the lighting in order they will move on getting the licenses right for both the vehicles by weight class and the drivers licenses by weight class of vehicles in combined usage, lots of variables from state to state on this one too. We are going to see a lot of changes as truck owners/users. I have a car-type plate on my truck issued here in NM, it has NO reference to weight class. It actually might become illegal to drive in other states that issue plates based on weight class regardless whether it is considered valid here in NM. It certainly becomes illegal when I hook a trailer in tow in many states already. There have been several guys here and on other sites that have been ticketed regaring the plate and it's weight class.
CD