Cuda rear sway bars

Hello

I was wondering if anyone has ever run an aftermarket 7/8" rear sway bar and used the stock whatever it is rear sway bar also?
The large one mounts down below, the stock one mounts up higher closer to the gas tank.
Any reason not to use both if possible? Over steer or under steer?
The front is one inch aftermarket.
This is a '73 440 clone Cuda.

Thanks for any info you might have.