Also I don't think 1990 was the last year for chrome bumpers as they are still illustrated in the 1991 brochure: https://www.picclickimg.com/00/s/MTIwMFgxNjAw/z/ru4AAOSwVehcmn
And in 1992 as well: https://www.picclickimg.com/00/s/NjQxWDEwMDA=/z/ApUAAOSwqpBdZXCY/$/1992-Jeep-Book-Sales-Brochure-Wrangler-Cherokee-Comanche-_57.jpg