No. Thunderbolt is a newer bus architecture that is not found in the older Mac Pro models. This means that Thunderbolt is not incorporated into the Logic Board and cannot be added. To properly connect a Thunderbolt interface, it will require a newer computer that has native Thunderbolt support.
Here is an image of an older model that does not incorporate Thunderbolt:
Here is a newer model of the Mac Pro that does incorporate Thunderbolt: