That's not a 1970 grille. There were 13 horizontal bars on the 70
grille. The grille you have pictured only has 4 horizontal bars. Plus
the grille was steel in 70 - not plastic.
Try having a dealer run the part number.
Looks more like a 80 to 92 vintage.
05 Park Avenue 36,055
91 Bonneville LE 306,191