The GM Strike of 1970 caused the delay of the new mid size cars for one year, so what was intended to come out for 1972 actually debuted one year later as 1973 models. All of the corporations mid sized cars were affected, so of course Buick was no exception, The 1971 styling continued for 1972, prolonging the availability of the convertible for one more season, until the new cars appeared for 1973.
Mechanically the car was little changed from the 1971-72 GS. The lowered compression ratios of 1971 had effectively stopped further engine development, so the engines were largely carried over for 1973. Both 350 and 455 V8s were available, as was a 455 Stage 1. The 455 was now rated at 250 HP, and the Stage 1 which developed 270 HP net. This figures are comparable to the net horsepower ratings of the 1972 models.