I have 100lb springs with billsteins What is the right preload or perch height?

A friend gave me a set of yellow springs with no markings.
Anyone know what they might be 140lb, 180lb???
They are pretty stiff. I tried them and they made the care feel out of balance. I would need to upgrade the torsoion bars to match. But what would this be??

You won't know until you try it. It depends on what you want for a ride height, the actual spring rate, how tired the springs are, etc... Try it on one setting, get the car back on the ground, roll it back and forth to settle the suspension, and evaluate. Repeat as necessary.

I went to a dirt track supplier and they had a spring tester. $5.00 and you know what kind of springs you have.

I have gone to the fourth perch on the billsteins. I have found that the rear likes to be slightly higher than lower than the front. This has been a lot of trial and error prosses. balance in the suspension is quite an art. but Iam getting really good at doing ther rear struts.

Iam trying to get a good street ride