Replacing rear leaf springs

[mrtexas]

What is the safe procedure to use to replace the rear leaf springs on a 49?

I've replaced buggy springs on a 36 but not parallel leafs on a 49. I suspect the rear springs are worn out as the car sits out of level in the front. Temporarily I have cut 3/4 of a coil out of the passenger side but would like to fix the real cause of the problem. BTW how can I make sure the rear springs are causing the problem. Would hate to replace the rear springs and the frame is bent or some other problem.