Does anyone have stiffer stock springs for the rear 84-87 suspension for sale? If so comment or pm me

I have a set of Stock rear springs from and 86 coupe, but I don't know how stiff they are. I'll include the rpo code data in case anyone can get the stiffness from that.

According to the rpo codes:
F41 - suspension, heavy duty, front and rear
Y99 - rally suspension package
8WY - left rear spring
9WY - right rear spring

I have a set of NYM code springs

Idk any of those codes or the spring weights for them. All I know is I installed a 3800sc and that weighs a bit more then a 2.8. When going into a corner the back of the car squats down a **** ton going into the corner

I don't know what the codes mean in terms of spring stiffness either. I was hoping someone else who does know would chime in.
Are you opposed to going to coil overs? That's what I did on my swap and on my stock V6 as well for that matter.
Then you can pick exactly the spring weight that you want for your setup.

There are no known actual spring rates documented.

REAR SPRINGS:
(EXC WS6) CODE (W/WS6) CODE
-------------------------------
1984 10029092 NWY (Stiffest)
10029091 NWX |
10029090 NWW (Softest)

1985-87 10030180 NXD 10034976 NYM (Stiffest)
10029092 NWY 10034975 NYL |
10029091 NWX 10034974 NYK |
10029090 NWW 10034973 NYJ (Softest)

from http://www.calgaryfieros.com/OSGdocs/springs.html
so when you say stiffer you are going to figure out where you are at and find your current code. If you search around theres a post on how to decode them from the fender tag instead of hoping the tag is still on the springs.

[This message has been edited by skywurz (edited 01-14-2021).]

If you really want stiffer springs, you ought to look into Fieroguru's coilover kit. Based upon your setup, he can even make recommendations regarding spring rate, etc.

https://fieroguruperformance.com/?page_id=267