In case you missed it in the Aug. '08 issue, we did a feature on installing Mopar's JK Rubicon Dana 44s in a YJ Wrangler. Complete JK Wrangler Rubicon Dana 44 axle assemblies are a great deal for those looking to upgrade their front and rearends. They come complete with disc brakes, electric lockers, and 4.10 gears and are a bolt-in deal for JK Wrangler owners.
Our friend Eric Maughan of Wellsville, Utah, ordered his Mopar JK Rubicon Dana 44 axle assemblies from 4 Wheel Drive Hardware and installed them under his '91 YJ Wrangler. In the Aug. '08 feature, we showed how Eric removed the JK bracketry from the axles, welded on spring pads, installed the ARB Air Locker switches for locker operation, and adapted the Mopar harness he got from 4 Wheel Drive Hardware that has the correct electrical plugs needed for the electric lockers.
Eric also installed a 4.3 Atlas transfer case from Advance Adapters. Mount Logan Off-Road supplied its super-strong aluminum tie rod and drag link. The guys at Tom Wood's Custom Drive Shafts rebuilt and modified the front and rear CV driveshafts to work with the Rubicon axle assemblies and also sent a pair of their JK Dana 44 pinion flanges.
Eric's YJ uses Rubicon Express spring-over leaf packs and also has a Vanco hydroboost system for the brakes. We mention this as his swap won't be exactly like yours, but it did show how relatively simple it is to do.
Both Mopar JK Rubicon Dana 44 axle assemblies are complete brake-to-brake and ready to bolt into a JK Wrangler. That includes 4.10 gears and electronic locking differentials. 4 Wheel Drive Hardware's part number for the frontend is P5153825, and for the rearend it's P5153826. Eric had Mount Logan Off-Road install 5.13 gears front and rear and strengthen the front housing by pressing in DOM tubing. | 
The Rubicon Dana 44 frontends have another weak point. The inner knuckles sometimes bend where the top of the "C" meets the housing. Eric gusseted them for strength. | 
OE JK Rubicon brake lines were adapted to the YJ. |