65 Mustang rear spring rate?

[DLinson]

I need to get some new rear springs for my friends 65 fastback. I built a 4 link rear suspension for it with a panhard bar with QA1 coil overs. We just used the "recomended spring vs. weight" chart in the catalog to pick the springs. It called for a 130# spring and it turns out to be way too soft and bottoms out a lot. I was thinking of going with a 170# spring. Do any of you know the factory front and rear ride rates for the 65 Mustangs or even a reconmended rear spring rate? He still has the factory front suspension up front. It is a factory GT small block A-code 4 barrel 289 car. We are hoping to change this to a MII suspension next winter but would like to fix the rear spring rates now so he can drive it this spring.

Thanks,
Dennis