There are two directions you can go with lowering. A) Slam it down low for vanity and have it understeer like a dog and ride like a horse and cart, caring stuff all about spring rate and having it sit on bump stops. or B). Keep the std spring rate (do not be tempted to alter or put in “whatever”. Std rate is about 110-120lb/in. While I would not condone cutting springs for “road use”, you can take perhaps one coil without losing all bump travel. The rear needs the rate increased two or three times std rate. About 450-500 lb/in should do. Custom springs are expensive. Depending on how handy you are a coil-over type spring in 2.125" or 2.5" diameter will work and you can use base adjusters to set height and corner weight. Can’t remember what length, I might have a pair (Mr Evil has a set the right length that I put in his car). Really to lower a decent amount you need a shorter front strut. Here’s one of a pair I shortened for Frankenstein’s Mira (it’s not welded yet)
note how short it is. This allows bump travel. The chrome shaft also gets machined down, I made new bronze bushes for the top and we went up in shock oil to about a 15wt instead of what was prob 2.5-5wt. All a bit of a stab in the dark from experience, but it was the right direction and did improve braking and handling. See my build thread for the Koni I shortened. I’ve done a lot now but have not bothered to document the process of shortening. Have a rear set to do next week. Note that rears to suit can come from Hyundai Excel with some good options available from the Australian Excel race series being a reason for manufactures bother making high end items.
You choose: have some joy driving it; or, build a static display.