Safe RPM for a 408" Magnum?

My main concern is with the pistons. I will never, ever use a hypereutectic piston in a longer stroke engine because the peak and mean piston speeds in a 4" stroke engine get very close to the limits for them.
I can't see a cam that short making steam above 6K. Peak torque is probably down near 3500 and stays flat, with horsepower around 5500. Raising shift points is pointless givent he cam whether you think it or not. Fix the transmission shift point rather than adjusting the limiter.