rough hammer design

Any particular reason to design your own rather than using a proven in design?

I have almost everything to build a krusty power hammer but I ran into a small logistical error. I've been trying to get the leaf spring but I need a make and model of the vehicle they should come from? Any ideas? They need to be straightened out to 39" so I need to know exactly what leaf springs to get.

thanks everyone 

There are spring shops that custom bend leaf springs and could probably make you exactly what you need. If you know what you need. 

The whole Idea of the original Rusty was to build it out of whatever you could find/scrounge and modify the plan as you go.  If you have to copy an exact plan why not go with a better hammer like the tire hammer?