A redesigned SN-95 Mustang came in 1999. Characterizing the redesign was Ford's New Edge design language, which featured sharper contours, larger wheel arches, and creases in the bodywork, replacing many of the soft lines of the previous model. The Mustang also received new wheels and hubcaps. However, the car carried over the same roof line and interior, in addition to the same basic platform.
The 3.8 L OHV Essex V6 returned as the base engine for 1999. A new split-port induction system replaced single-port induction, which increased the base model's output to 190 hp @ 5250 rpm and 220 lb·ft (298 N·m) of torque @ 2750 rpm
The Mustang also received a change to its taillights, making them edgier, with sharp corners and straight lines as opposed to the rounded off style of previous years. The lamps were still composes of three vertical segments, reminiscent of the original.
Source: Wikipedia, 2012