SS leaf springs de-arched

I bought a 68 Dart with SS leaf springs and would like to lower the back down to my liking.

If I take off the SS springs and have them de-arched to lower the rear of the car 2.5" does that ruin the leaf spring for racing purposes? Anybody else done this with there SS springs?

Also considered using a lowering block or just putting some 40 year old 340 car springs in the back.