The braces behind the rear seat will do you more good than the front lower brace.
You did not respond to RacerX comment about the bushings. I would check not only the front A-arm bushings, but also the body bushings. The most important body bushings are the ones below the fire wall. These take the most loading.
Also, check for the missing bushings (4 each) along the frame in front of the rear trailing arm connection point.
When you install the missing lower bushings also take the time to install the GNX rear top bushing located above the rear differencial.
Conclusion: Spend your money on bushings and rear seat brace before the purchase of the front lower brace.
Deep Enough
Donald McMullin