Various letters are found on the third line of the trim tag. These include:
X & Z: Sometimes just the X, sometimes just the Z, sometimes together as XZ which are found on 131/132xx Nomad series and 133/134xx 300 Deluxe series.
L: Probably the most controversial is the letter L found on 300 Deluxe (along with X) and Malibu series Chevelles. It's strongly believed this letter L indicates external SS396 trim but this has NOT been confirmed by any direct knowledge or GM documentation. The letter L has been found on at least 1 non-SS396 optioned Malibu and at least 1 known SS396 optioned Malibu has been found without this letter L. While using this letter as a way to determine if your 1969 Chevelle is a true SS396 or not is up to you, there is no 100% guarantee but there is strong evidence that it does.
