I know that 97 was the last year for the aluminum (CHEVROLET) band on the Chevys. I would thing it is the same for GMCs, but IDK for sure.I believe they were only on '88-'91 trucks as well. Very rare to see.
https://nemigaparts.com/cat_spares/epc/chevrolet/52c-c/17/tzc17-03/