Last I heard the longest extension recommended off a stock hitch is 18". This type of extension also reduces the dead weight rating of the factory hitch by 1/3. 5000lbs minus 1/3. The Torklift Superhitch and Torklift Magnum SuperHitch can do what you're asking. The Torklift extension will also handle a weight distributing setup upto 48". You might have to upgrade the tires to 19.5" commercial grade tires/wheels. I run them on my truck. They add an enormous amount of stability. Also look into the Torklift stableloads.
93' YJ w/factory hood