I'm getting a kit (used) for the stock unthreaded billsteins on the front. My question is what size inside diameter springs will I need and where can I get them?
Which kit are you getting? Maximum motorsports uses 2.5" coil springs on their front coilovers, as does MMR. MM has a ton of springs on their site.
If you are setting up your car for drag racing, let me know. I have a set of 12", 175# springs that are great for dragging. MMR sells them with their street/drag coilover kit and uses them on their drag car.