You need one on each side. There are separate threads concerning the LCA. The lower control arm is a different length from the upper control arm so as the axle moves down by installing longer springs, the axle rotates slightly to the front about its axis and this changes the caster angle of the front suspension, negatively affecting steering stability. A longer lower control arm will help restore the suspension alignment to where it should be. What we call the Mopar LCA are longer lower control arms that come with the Mopar lift kit, but they can be bought separately and they are not expensive, however they can be a pain to install. There are some aftermarket manufacturers that sell adjustable lower control arms so you can dial in the suspension alignment that you want.First off, I want to thank everyone who has responded. Such a wealth of knowledge and experience, and not having to sort through a salesman trying to sell you on something you might not need. Given the responses, I might try checking out OfferUP, Craigslist and Facebook Marketplace and start with Rubicon take-offs and spacers. And see about ordering the LCA (long control arm?) to put on. Is it just one control arm that I would need?