[rotorwrench]

As a general rule, these suffix's are engineering or design changes. A lot of the FoMoCo parts are utilized for more than one year model and many parts are modified to improve fit or function and also reduce warranty concerns. Some parts have multiple changes too such as carburetors that are set for higher altitudes and rear axle gears that have different ratios and the like. In body parts, it can be a part that uses a slightly different assembly due to several sub-vendors or even a different color or color combo of interior trim pieces.