Does the TV have Width and Height controls? If so you may be able to redude the image size so it doesn't overscan. If not, see if there are Underscan or Overscan settings in Displays system preference.
If these don't exist, try SwitchRes
A.C. Paschalis wrote:
The Mac Pro recognizes its resolution immediately. The only problem is that I need to callibrate the screen size because the OS screen is outside the TV's visible boundaries.
This sounds like overscan. Over the forum, we can't guess whether it's because an Overscan option is on in the OS X Displays preference, or because of a display size setting on the TV. You'll have to check both.