Although you may be entering a speed class that would normally allow U-rated Tires, most tech inspectors know the Pantera came with (in many cases) V-rated tires.  In some rule books this means the car must have the minimum rating the car was originally sold with...   so you need at a minimum V-rated tires on your Pantera, even if you are entered in a lower speed class.  And remember, the tech inspector's word is final; they have the responsibility to approve the equipment used during the race.  They do not want the liability involved with approving a lower rated tire than what the car can handle and having someone exceeding their speed bracket, blowing a tire and causing an accident.

So don't dicker with them, just put V-rated or better tires on that meet or exceed your speed bracket.