Kirban rear variable spring rate

[michael evans]

I know they don't make the 1520-Buick spring anymore but I am replacing them with coil over springs but I am looking for the rate of them.

 

[1986 Buick GX1]

I’ve read the springs for the T-type package are 422 lb/in. for the front and 118 lb/in. for the rear.
The UMI Performance springs are 600 lb/in. for the front and 130 lb/in. for the rear.

It seems the regular regal springs were like 355 lb/in. for the fronts, but I don’t recall reading what the rears were.

Hopefully someone will chime in with specifics on the 1520 springs.