My freshly redone BBC 454:
-LS 6 shortblock
-Comp Cams XE274h cam
-GMPP oval port heads
-Performer RPM manifold
-Holley 870 Street Avenger carb
-Holley 110 gph Mechanical fuel pump
-MSD 6A
-Dynomax 1.75 headers(full 3" exhaust)
will not rev past 5600rpm.This is basically the same engine configuration that Car Craft magazine put together that made over 540hp and 560 ft/lb of torque.
But this thing of mine starts to stutter and miss like it has a rev limiter at 5600(yes I have tried different pills in the MSD but no difference),but once you shift and the rpms fall back ,it pulls strong again until the 5600 mark again,then POW missing again.

Very frustrating.Suggestions???

are your valve springs correct for your application and in good shape. I would look here after completely checking the ignition system.

Valve float could be a problem, but I'd check the fuel system also. Are you using a high volume pump? If so, and if the pressure output is okay, then you should check the system from stem to stern. Check everything from the fuel sock in the tank to the filter at the carb. Check all the lines, especially the rubber hoses that connect between the tank and steel lines on the frame at the rear of the car and the one from the frame line to the fuel pump in the engine compartment. Make sure they're not cracked and brittle and causing air to be drawn into the fuel system.

You might check the jetting in the carb. It may be too lean to run at high RPMs. See what the plugs look like.