Its Pedders std spring pack for around 35mm drop, sorry no part numbers anymore, but if you give them a call, they will tell you. Its an off the shelf front and rear matching combo. I did find the front dropped a fraction less than the back, does it affect my high beams, well i drive with them on many of times and its perfectly fine.
Overall im really happy with the ride front and rear, the handling is great, (ve sv6 was really good to begin with imo) but dont expect huge differences over the stock springs, all your really getting is better looks, posibly a fraction firmer ride, and when you get in the car it feels lower.
If you get the super super super lows, about 50mm drop, which youll also want to replace the shocks, then expect significant changes in handling,
somthing i didnt want to do, looks a tad better, but slightly more cost, and them speedhumps and curbs :S :S