Building the car for Autox and am looking into springs as a purchase in the summit. Car is an 89 RS V6 running in STS. After I get new front shocks the springs are next. What Moog springs would be the best to run with (part numbers and where) and what are the stock spring rates for me?

 

Just the V6 in the car?
You can go heavier on the springs, but the car will ride higher and more rough. I'd (gasp) follow the advice of Dean, and stay with lighter springs and bigger sway bars.

Moog
5658 - 600lbs/in (I think!)
5660 - 650lbs/in
5662 - 700lbs/in
5664 - 750lbs/in

You probably have the lightest ones in there. The 5660 I believe is base level for the V8 cars, and 5662 is the WS6/Z28 style (I think). The 5664 is the stiffest moog springs that will fit in our cars. They're actually for S15 trucks, or the 3rd gen convertibles.
I'd go to a 5660 and take a close look at your front sway bar. Upgrade the size and put poly bushings on it. Look at a strut tower brace and wonderbar and SFC's of course.

The moog springs can be purchased from your friendly neighborhood auto parts store.

 

look at summitracing.com
They have two MOOG's for the front of the V6.
A 347 lb, and a 421 lb.
Id stick with one of those two, go 421 if you want stiffer.
If you want even stiffer after that, get some Nice struts,
Adjustable KYB's/ Konis's Or tokicos!
Do the rest of your suspension
(sway bars/ wonder bar/ panhard/lca's/SFC's/bushings/Endlinks)

Dont go with cut V8 springs, or lightweight V8 springs, unless you
want a funky riding camaro that will shake the teeth out of your head!

 

I already have a wonderbar and 36/23 swaybar combo (from a WS6) with poly. Going to get Konis on the front and already have Bilsteins in the rear. Springs/shocks and bushings will do it for suspension. I want to stay legal in the STS class so no SFCs yet.

 

These links should help you.

https://www.thirdgen.org/firebird_spring_rate
https://www.thirdgen.org/camaro_spring_rate

http://bbb-carb.com/moog_Coil_Springs.htm

 

Got these springs and will be putting these in this wekend. 421lb in the front and 104lb progressive in the back. Is there any other parts that I should pick up that need to be replaced with the springs? I'll be doing bushings down the road.
http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku