Your going to get this a lot but I would just hold off till you do have the $$$.I just bought my gt in jan and it had cut springs,ride was terrible.I put the pro kit on and it rides great now.If you are set on cutting them then I think the common is coil.Good luck.
Try to find a used kit on the classifieds. I would not suggest cutting them. The factory springs, like many aftermarkets are progressive springs which means they get progressivly firmer as they compress. This allows a good ride but still has plenty of controll. A specific rate spring is a spring with one rate all the way from relaxed to full compression, these springs you can cut, but the side effect of them is that you will either have a really bouncy soft ride which can get real squirelly and won't ride good, or rock hard and won't really perfrom that great either. When you buy springs, be sure to know what your getting.
If you cut a progressive spring of the soft side, you will get a rock hard ride that won't perform too well becuase a suspension is suposed to have some give to conform to the road. If you cut the firm end your going to bottom out a lot and be all over the place.
Save your money for now. Make sure you have good struts and shocks, they can make a huge difference in both ride and performance. R&R springs, cutting them... thats a lot of work for crap.