Steve,
There are several ways to "etch" glass. One is to cut it with an abrasive wheel. This is really expensive and each one will be slightly different because they are done by hand. The other methods involve using abrasive materials or acids. Since no one around here does acid stuff, and frankly I have only heard of this method, I had to do it by the abrasive method.
If you are in or near a city that has some glass craft abilities there are ususally several shops that can do this work. What they do is to make a pattern for your design, and then apply it to the glass. You remove the positive or negative portion of the design depending on whether you want the image to be etched or the background to be etched. With the mask image in place, the glass is then etched with silica. The resulting effect if done right is nothing short of beautiful.
To answer your specific question, the outfit that did my clearstory windows here in Nevada was Ultimate Glass Studio. Their telephone number is:702 388-8841. The designer is Phillip Razavi. If you already have a pattern from the old car, they can reproduce it. I had an old design that I wanted to use, gave them a xerox copy of it and bingo, they got it exactly right. I might mention, when I was in their shop there was some Doctor there who was building a house for $12,000,000.(Boy, he must have one helluva a practice). He was having these guys do the glass etching and carving for all the windows and mirrors in the house and it was absolutely eye popping stunning!!!
Hope this helps.
Dan