I was the one that did the 3.73 swap on my buddy's 05 3.7 liter Grand Cherokee WK. You need to get a front differential out of a 4.7 liter with 3.73's and QT II. You will still use your stock cv axles. As for the rear we used Motive gear 3.73's for a chrysler 8.25 axle. The dealer can't do the reprogramming, but the Hypertech speedometer calibrator will be able to reprogram for the gear change. It's an easy sway if your familiar with setting up gears on a 8.25 rear axle. You will still use your original transfer case. No issues with his Jeep since the install.