Have had many suspension iterations on mine. In the spirit of "the best way to spend a TON of money is to have to do the same job 2 or 3 times because you weren't happy with the parts you picked the first time..." I'll offer this.

I went with Kaplhenke Racing parts from Ben Kaplan up in MD. Absolutely first rate stuff -- I think the best engineered product on the market. And you pay for what you get -- it's not inexpensive. But you won't find anything better. And I finally got a set up that works the way I want it to. NO COMPARISON to using stock sized "sport" springs from IPD and others.

Mine has Ben's adjustable coil overs on the front - Eibach 275 lb/in springs, Ben's adjustable spring perches on the rear with Eibach stock diameter 200 lb/in springs. Ben's "Luxe Steer" strut bearings, roll-center correctors (correct the roll center due to lowering the car), Ben's caster/camber plates, Koni Sport dampers, poly bushings all around, reinforced rear lower control arms, IPD 28mm front "drop" sway bar and no sway bar in the rear. With 440 lb-ft of torque, and a bit of roll stiffness from the rear poly bushings, no rear bar desired (which shaves off weight!). I also kept the ride height where I don't have to dodge driveways and such and didn't have to cut the front strut tubes. I think front springs are 12" free length and 2.5" diameter. Rear are 14" free length and 5" diameter.

Car is firm/taut -- I think it rides better than it did with IPD springs and Billy HD's -- all bumps are one and done. It's not the least expensive option - but I'll promise you, you won't be second guessing yourself.