The Amarillo package only came with black leather interior. The brown leather you are thinking of is in a king ranch.
The Amarillo package was available in the southwest in the 05 model year but it did not have all of the interior upgrades that it got in the 06 model year which was sold all over the country. The 06 Amarillos were only produced in the first 3 months of production in the 06 model year then they stopped making them and started making the harley davidson trucks.