I have a 91 cherokee and I need to replace the grill. Can I use a later model grill or will it not fit.

You could go to your local Jeep dealer and ask someone who has been there awhile what they would recommend doing on a replacement grill. You might be able to get a grill to fit from say a 92 or 93 as most of the Jeep body styles didn't change drastically for about 3-4 years. I have a 94 GR cherokee that a grill from a gr cherokee of say 95 or 96 or 97 would probably fit. You could probably ask a junk yard as well as most individuals who work in junk yards generally know which parts are interchangeable from one year to another. It's amazing just how much knowledge junk yards have. They also have an interstate or instate service that can locate you a 91 grill as well. Check with the bigger junk yards for the best deals.