I built my own t-arm/panhard system
www.dariusrudis.com (website down for the moment?). The ground clearance under the axle is no big deal. You will be using the tires to go over the bumps anyways (which lifts the axle over). Ground clearance for the exhaust... is the concern. I run a custom sidepipe exhaust system instead of turndowns.
As for the Steeda piece, its awesome. I run with one of the guys that heled engineer it. Great bolt-on piece, and wont be disappointed. Pricey - yes, but definitely worth it.
For install ease (at home) I would recommend the Steeda. The the Griggs (flat out works!). Then for street duty, recommend (or merely suggest) the maximum motorsport t-arm.
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Darius Rudis
Roadracer: Home built t-arm/panhard suspension powered by an S-trimmed motor :-)
My Mustang Page