This is what I would do. Install the distributor, get your timing tight and tach. Run the car and watch the timing for advancement. At first sign of advance record that rpm down. Then raise your rpm's up until there is no more advance then record that rpm number. Then you will know the rate of advance for those springs. At that time you can decide if you want stiffer springs or loose springs. Or if you want timing coming in earlier or later. I have done this process I bet a hundred times, it can't go wrong. And another thing. You are going to need a dial back timing light or have a balancer with marks up to 50 degrees or more or,, timing tape on your balancer for this to really work. Or not!