I would regear your diffs first. Your Jeep will be more enjoyable on road as well. The 3.21's should never be available but many Jeeps never make it off road so a lot of people don't realize the gearing shortcomings. There's a gearing chart (just do a search) that will help you out. I run 3.73's and I feel like I need a regear so I am sure 3.21's are frustrating out on the trail.
2014 Mustang GT Track Pack
2015 WK2 Limited 4x4