The unfortunate reality is that it is very unlikely someone is going to have a set just sitting around to take measurements from. You have either not purchased them, or have purchased them and already installed them. They are in such a location that it is impossible to take measurements once they are installed. This question comes up regularly on the Mustang Forums. They are not as easy to make as they appear to be. They can only be made efficiently in manufacturing environment. From the start you are looking at burning up a quarter roll of welding wire, that's a couple bucks, and you are probably going to wear out two drill bits, and that's like $30 right there. Plus the cost of the steel. Even if you use scrap steel, you are going to spend a lot of time prepping it and finding the right odds and ends to use. You're looking at spending half a day making these things to save $20. Ask yourself how much your time is worth to you? Heck, I wouldn't be surprised if it took you a whole day to make them, and that's if someone actually gives you good dimesions from the start.
Kurt