I pulled up some photos from the web of both a GMC and a Chevy Suburban from 1989 and they look to be the same size and shape, but the GMC design is different and looks like it may stop short of the headlight housing. It probably comes as one big piece, but you may want to look into that.
I also found some aftermarket companies that appear to suggest that the GMC and Chevy grills can be interchanged, but they want to see you everything, including the headlight housings.
There may be differences between the 1500 and 2500 Suburbans too.
As far as I know, the grills up to and including '91 were 3-piece grills: a center section with the emblem, and 2 side sections that was just large enough to house the headlights and running lights. That makes it real easy to change a headlight.
I actually have a grill for an 89 GMC Suburban sitting in my closet at home. It doesn't have the GMC emblem, just the grill section. I just sold the Suburban and never installed the new grill. I really don't want to ship something that big, but if you are local, we can work something out.
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