do i need a pvc valve and breathers on both valve covers.from what ive seen in the magazines it looks like most people are running to breathers.and is there any performance diffrences between the duraspark and the dura spark 2. does it matter which one i use. i have a stock 84 distributor.what would be a good carb. for a 306 ,f-cam,202 160 valves with 1.72 roller rockers,edelbroke rpm manifold