Mercruiser 383 STROKER SCORPION BRAVO 400 HP! 

It is kind of a misnomer to say that this was designed in the 50's. It would be more accurate to say it was designed in the 90's because it is based on a 90's chevy small block. Sure it does share some elements with the 50's small block but everything on top and inside of the block is way more modern than that.

having a better bottom end and different style intake allows for more rpm on these motors

When bottom end is balanced and built properly, camshaft duration, cylinder head flow, intake flow, and exhaust flow play a huge role. Piston speed is the biggest limiting factor of an engines redline though.

Billet steel hydraulic roller. intake lift 0.575" exhaust lift 0.596. it doesn't list duration

5.7

Drops your RPM and reduces your operating RPM and unless you are using forged rods the engine geometry is not good for 6,000 for any extended amount of time. Even with pink or dimple rods. 6 inch rods would solve the problem. I think you are going to get a lot of blown engines. Even with 1 gram balanced, polishes and shot peened rods.