The average 408...

Mad Darts heads brought your combo up 20HP - 446 @ 6000

Mad Darts cam hurt the Dart/WCG combo - down 6 HP

Mad Dart also runs an SP and large tube open, so.............

Your heads with with SP, Open big tubes, MDs cam runs:

486 @ 6000

Use MDs heads as well - 516 @6000

Result

Your cam seems ok, your heads are not doing it - probably because your intake is crap and your headers are choking the whole deal.