You can do a 'Low Buck' SOA on a YJ for around $1000 or less. Granted, the steering won't be perfect (Get a better axle before investing in Highsteer) and the stock leafs will fatiuge faster than lift springs, but all that can come later. (Later, like when you swap in real axles, and get bigger tires. Because you WILL get tires bigger than 33's...... Relax.... just let them come naturally!!)
Invest in a quality SYE Kit, and do a SOA using stock YJ rear spring packs. Use a Dropped Pitman arm, longer brakelines, and appoiate shocks and enjoy the flex. You don't have to add the Traction Bar right away, but plan on doing it soon after the SOA is done. Change the rear U-Joint Straps to U-Bolts ASAP.
I did a cheap SOA on my YJ and it rode and flexed killer! Heres mine on stock Springs and 33's-