This may be a stupid question but what determines a motors max RPM. Is it Cam or Heads or both? My 454 is wound out at 5500 rpm. Does this mean it has a low duration cam?

There is a misconception out there that more rpm = more power. Not quite true. Many engines will rev past max power rpm. There is no reason to do this. The only way to determine peak hp rpm is a dyno.

Since an engine is nothing more than an air pump, if more air can be passed, more power can be made. This requires a careful balance of camshaft profile, cylinder head and intake flow rate. As flow rates increase the rpm that power peaks at generally increases also. But there is a big trade off in that high-rpm engines are usually sluggish at low rpm, have rough idle quality, get lousy mileage and require low axle ratios. The 360hp 454 was a great engine for general driving and had decent power. The LS-7 454 was miserable in daily driving but had awsome power.

Depends on what you want and what you can put up with.