I have the PA Racing one - it's a nice piece. You need to decide if you want to run stock shocks/springs or go with coil-overs. The guy from PA-Racing suggested I stay with stock springs for street use. Either way, I'd get the dual-setup that lets you do either.
I might have a problem though.... I put on the Global West springs from John Pearcy. I didn't think they were lowering springs, just stock replacements. With PA k-member, the front end is very low over the front tires without the motor in the car. I'm a little concerned.... I hope the motor doesn't cause the fenders to bottom against the tires.