I have the TRD springs on my car, they lower apprx. one inch. Thats allready pretty low with the tires i have on it, any lower and i risk banging into the wheelwell on bumps. So really, I'd say that the lowering question has alot to do with how firm the shocks are going to be, and what size tires you are going to use.
Here I have a picture of the wheelwell, so you can get an idea how little space there is there allready, ive never had a problem with the wheel bumping into the wheelwell, but that doesnt mean ive come very close and not known it. My suspension setup is with tokiko 5-ways and trd springs. I have no idea what that means in terms of rebound though.
Thanks for your reply. I ended up buying some Australian made king springs which have lowered it about 1 3/4 inches. It now sits just above the tyre on stockos. BTW 4agze, your car looks really nice. Youve done a really good job. Bet it set you back a bit. If mine looks like that at the end id be really happy. I started with the engine bay and converted the blown old stocko 4age with a 4age 20 Valve. Havent been beaten by much yet. Ill get some pics on a site soonish. Cheers