#479381 is the 70-77 plate.
Radio delete panel 70_77 479381 by
Ben, on Flickr
#10001245 is the 78-81 plate.
GM 10001245 radio delete 78_81 NOS by
Ben, on Flickr
A 70-77 radio bezel will obviously work for dimensions.
https://cdn.classicindustries.com/as.../F/F117077.JPG