I'm not familiar with the LS29, and google isn't helping.
If the car is going to be low, the 9" has a lower pinion, so it's easier to get your driveline angles set correctly than it would with a 12-bolt.
I'm not a fan of Hotchkis... their spring/shock combos work well, but I don't like their front end geometry or their rear bushings... they offer 2 types for the front, which is stock spindle (backward camber curve) or the B-body spindle, which corrects the camber curve, but messes up the steering geometry. The rear arms use poly bushings in all 8 points, which induces a roll-bind condition, making the car's balance very unpredictable. I'd recommend checking out either SC&C (
www.scandc.com) or Detroit Speed & Engineering (
www.detroitspeed.com)