Originally Posted by Onsit

If possible you could probably source someone's OEM suspension that has upgraded to aftermarket coilovers. However you should be able to reuse the OEM springs, tempered steel doesn't exactly degrade in the same lifespan as a valved strut assembly. Buy new Struts, compress the springs, and reuse your tophats. On the IS300 the tophats do not have pillow bearings like other Japanese cars do so you can reuse them for quite some time.

On my IS300 I opted to liven it up with Eibach springs, and Bilstein struts. It's very planted, responsive, and coincidentally what the L-tuned version of the vehicle came with.