The adjustment is in the rod between the bottom of the shift lever and the transmission bell crank which goes through the NSS. There is at bushing at each end of the rod. The bushings get brittle and disintegrate throwing off the alignment of shift lever and transmission. If your bushings are damaged or non-existent, fit new bushings before replacing the NSS. Don't change the length of the rod unless you mess with the transmission or shift lever.

Sixto
87 300D