What weight springs for coil over shocks
 

So I am looking at coil over shocks for the front of my 64 El Camino with a small block motor but am not sure what weight of springs to get ? This car will be driven around town mostly and occasionally some spirited canyon carving and maybe once a year autocrossing . Should I go with the 450 pound springs or the 550 ?

I'd go with the 550's. A heavier spring up front will transfer more weight to the rear. You might like the extra grip back there when your canyon carving.