A popular "Go-Package" option came with either the four-barrel 343 or 390 engine and included power-assisted front disk brakes, "Twin-Grip" differential, E70x14 red-stripe performance tires on 6" wide steel wheels, heavy-duty suspension with thicker sway-bars, heavy-duty cooling, as well as other performance enhancements.[1] A wide range of specialized performance parts were also available through AMC dealers for installation on customer's cars. These were known as "Group 19" parts because of the way AMC organized its parts books.[38]