410 LA small block will not rev past 6000

Two things come to mind for this issue. While there could be others, y questions are;

Are the valves springs installed at the correct height with enough pressure?

Are you sure the valve train is right on the geometry?

The Springs were shimmed to get the pressures Hughes called for 145# closed and 350# open (at 0.550 lift) they were very close to those numbers. I could always throw some more shim under them to get some more pressure that would not be too hard to do, the cam only has 592 max lift on the Exhaust side so coil bind should not be a problem Coil bind not till .750".

The lifter preload was measured and set to what Hughes recommended.