I'm not sure if you can even get lowering springs just for the front. They usually come in a 4-wheel set. Although if you're patient, you may find some used ones in the Mall, or on eBay.
That said, Rodney Dickman sells lowering ball-joints for the front suspension. And they're relatively inexpensive ($69 a pair, plus shipping).
I went from a 2.8 to a 3800 and there was no discernible difference in ride height in the rear. I have since gone with Eibach lowering springs front and rear. I think the above statement is correct and they're always sold in 4s. The springs cost me about $300 with shipping to Canada included (plus about 1/4 pound of skin off my knuckles installing). They're all over eBay at prices from $240 - $300. Ended up in a ride height reduction of just under an inch, pretty much all I was going for. Any lower and I wouldn't be able to reach the door handles without crouching
Or you could get coil overs for the rear, drop spindles or ballpoints, and cut a coil off your front end springs. Not quite as comfortable but at least you have some adjustment, and save some cash for front coilovers
