[HCO41]

I'd like to open this subject again. Earlier in my career I worked for a large cutting tool manufacturer. One of my jobs was creating the specs. For "special taps". We manufactured Carbon, Cut thread and ground thread taps. Since 7/16-14 is the thread size this thread is addressing, I can tell you that our blocks would have been tapped with a ground thread tap. Tolerances are much closer. I don't know what class thread Ford originally used, but I suspect GH-2, possibly GH-1. The ground taps we stocked in this size were GH-3. Carbon and Cut thread taps were tooled to this dimension, but tolerances were not as stringently controlled as the ground taps. (Carbon and cut thread taps are generally roll formed). Ground thread taps are classed higher or lower than nominal size and designated by GH (above nominal), GL (below nominal). Each limit (GH-1,2,3,4etc. and GL-1,2,3,etc.) has a tolerance range measured to the 4th place (ex. .0001-.0003). The taps purchased at our local hardware store or even industrial supply store would likely open up the threaded hole more than originally intended. I took a look at the rethreading taps on the link posted above and noted that there was no class specified. I would have to trust their intended use and would definately use them before a hardware item. If I still had access to special overruns, I would be looking for a 7/16-14 GH-1 bottoming tap.
Hope this helps for the future