I can tell you you want on a rear engine car to have a 200-300 lb diffrerential f/r due to the weight in the back, otherwise you will have an oversteer issue.
Springs are cheap but expensive to switch. The thing is you want to tailor your springs to the tires you use. for example when i run slicks i use 1000/1200 at least and with DOT-R 800/1000. your tire is part of the spring calculations.