extige=exige.
it is my understanding that for forced induction you probably don't want as much duration (well, really its overlap, but with that much duration you're going to have overlap). This is to prevent (especially on supercharged cars) the intake charge from being blown straight out the exhaust, without ever getting to see a spark.
You definitely want lower compression for any forced induction application, but more so on a L-series with its in-eficient 2valve technology. If you are doing a rebuild, go ahead and plan for the supercharger by dialing in a lower CR.
good luck!