I'm not convinced that a rear sway bar is a good idea on a solid rear axle car but that is a matter of opinion. Generally, heavier rear springs will provide the same effect without providing oversteer at the limit that a rear bar tends to induce.

Both of mine, which have stiffer springs all around, are definitely tail-happy at 10/10ths with the rear bar -- it's way too easy to kick the back end around with throttle. At 8/10ths, the rear bar gives the steering a more precise feel and turn-in is quicker.

The front bar is a must unless you drive on really rough roads a good deal of the time. The rear depends on how you drive, how much power is available, and a dozen other factors.