I'll throw my 2 cents in here since I just swapped my 2 stage 9 leaf spring out for a composite spring in June. I went with the 340lb TRW spring and the KYB low pressure shocks. Right out of the box I'll say that I was not at all happy. The ride height is way too high and the ride is now really bouncy. It does seem to have improved some over the summer however. The rear end is still pretty high but the bounciness has decreased slightly. I'm glad to have lost some weight in the rear end but I just wish I could get the ride right. If you are considering a composite spring I would also consider adjustable shocks. It seems to me that some tuning is in order here.

For those of you who are wondering about your original springs I have two words for you, metal fatigue. Chances of your spring breaking are slim but have you ever thought about what it would do to your rear quarters?

ricknhis69 said: ... The ride height is way too high and the ride is now really bouncy. ...

Longer bolts that connect to either end of the spring will give you more height adjustment than the original bolts. Every parts catalog I've looked at has had them.