I'd assume you already found the excellent info from Paul about there being a way to roll in USB3 drivers to a W7Pro installer build via a method from Intel. Here is that source thread, if you did not find it: Link
The "restore" builds that HP includes on the original drive or via DVD generally have important drivers custom added in by HP, before they provide that "image" to load from. I would contact HP directly to see if there is an option to purchase a W7Pro version for your specific model. There has been the option to officially downgrade from W8 to W7. This user's forum is not the official conduit for such requests.
A nice feature of such builds is that the HP OEM COA is included, and once you create a finalized build to your specific needs you can capture that image and clone it to other of your same-type workstations and that COA will work on them also. I'd personally want the 64-bit version, if available. Of course, check to make sure that all the workstations you clone onto have the legal right to use that COA.