Is there a spring upgrade from what the stock road runner comes with?
Roush has an upgraded spring that they use in their sealed 302R engine builds. Contact RPP or Ford Racing to find out more. Rehagen probably knows about this as well.
They can probably be had cheaper from a vendor on this site. I thought these were OEM parts, didn't realize they were aftermarket, but since they're "Ford racing" I suppose it makes sense. Certainly a lot cheaper than other options... probably designed for high RPM N/a, but not really boost.
http://www.cjponyparts.com/ford-rac...0l-4v-gt-boss-302-s-r-2011-2012/p/M6513M50BR/