This is kind of tricky.

Your front suspension doesn't use coil springs, but instead has torsion bars. You can get replacement torsion bars that are thicker which give the effect of a stiffer spring, and I believe there's a factory height adjustment but I'm not sure quite exactly how it works.

I believe there were lowering springs available for the rear at some point but I have no idea if they're still in production. The chassis is essentially the same as the '84-'87 Civic and CRX so some of the parts may be interchangeable.