Auto-X / Roadrace rear suspension 1969 Valiant

So I did a little math too. If the Hyperco's that the E-body guys seem to prefer are 225 lb/in, and the Hotchkis E-body spring rate is 160 lb/in, then for an A-body if the traditional spring rate should be ~130 lb/in you'd be looking at 182 lb/in for the Hyperco's to maintain the ratio established by those E-body guys. And my 121 lb/in AFCO's would translate to 170 lb/in.

Also, it looks like Speedway sells the 175 lb/in Hyperco's...
Hyperco 10203 Chrysler Composite Leaf Spring, 175 Lb. Rate