Rick Ehrenberg from Mopar Action advises against the U joint coupling because it has no fore/aft slide action. This could result in broken steering column capsules and worn bearings. I've seen and read of people using them anyway with few problems. Rick is like anyone else though. He has his opinions based on what he believes.
There are rebuild kits for the factory couplers. Steer and Gear offers an alternative to the thin steel retainer that seals in the grease: Its a polyurethane boot that fits over the end of the coupler. They are P R I C E Y though..... $28 each! I called to order a few, thinking that they might be $10-$15 each. I only bought 2 !