Just my opinion, but I'd probably buy a lowering leaf spring kit like the one one hotchkis offers. A few good reasons would be, you would have all new stuff. Good mounts, good bushings..ect. Also, they are better than stock for handling. And, the best reason of all IMHO, anytime I put something on a car "temporarily", it usually ends up being on there a lot longer that I first thought. At least, thats what happens to me.

You might as well get a good handling package in case your coil overs take longer to add than you anticipate. And heck, depending on your goals, you may even be satisfied with the lower kit and not even want to go coil over. Plus, you could probably recoup some of the cost of the lowering spring kit by selling it when you do put on the coil overs.