Problem with no 66 reverse lights

I have asked many people this question and I always get the same answer and it does not work for me. I have 3 66 mustang coupes. all strait 6 automatic, no power steering, all original. basically they are all the same except for one of them that has no reverse lights. I pulled this car out of an abandoned lot at found that is is in fact an all original car. I ran the VIN and it is in fact a 66 and looks just like any other. it has never been modified or painted any other color than the original blue. I have seen other cars with no reverse lights, but not many. some people say that the back valance has been replaced but i know this is not true. I have looked in parts magazines and some valances do not have openings for the lights. Why do some of these cars not have the lights and others do? I would be very thankful if someone go give me a logical answer. Not "the valance was replaced." I will not except that. PLEASE HELP!!  

Back up lights weren't around on '64 1/2 cars and even on some early '65 cars. Later in '65 they became optional. 1966 was the first model year they became standard equipment.
Some hot rodders back in the day removed them because they didn't look or seem performance oriented and they also wanted to save a little weight wherever they could.
It could be that the original owner of your car special ordered the Mustang with a back-up light delete statement in which case the assembly plant would use left over 1965 rear valanece stock to fill the order. He may also have had the local dealer agree to do the change locally before he accepted the car.
After all the Mustang was billed as being "the car designed to be designed by you". Seems that might be true for you car.  

Thankyou SOOOOOOOO much for the first logical answer I have gotten to that question. I did not know that you could have ordered the Mustang that way. IS there a website or book or anything that I can read to findo ut more information about options and codes for early Mustangs? All I want to do is find out all I can about my cars so I can restore them the right way. THANKYOU AGAIN!!!  

You're welcome. Always glad to help a fellow Mustanger.
There are many books out there that you can buy from Mustang resto vendors.
One is called the Mustang Recognition Guide that helps folks in the hobby identify certian features on each year of Mustang. It lists what was standard and otional as well. There are other publications that do the same. You just have to see which one has the level of detail you are looking for.
You might also consider contacting the Mustang Club of America and talk to them or a Mustang judge about special orders and delete options as I'm sure they have dealt with most of those questions in judging situations many times over the years.
Good luck and happy Mustanging.