I'm assuming you are wanting to lower your octane requirement? A longer duration cam would lower your cranking compression number but would reduce driveability as you would lose bottom end power but first (it'd be easier/cheaper) I'd get a multiple keyway timing chain set & retard it 4 deg & see what develops. As you know recheck valve to piston clearance when advancing/retarding as either the intakes or the exhausts gets closer & the other gets farther away. Not sure which would be more effective on what you are after either a longer duration cam or retarding your current cam cuz I ain't a cam guy but just me I'd retard your current one first. Holler how it turns out