AMC 360 Limited RPM?

To the original topic:

This engine of yours is not making much different power than a stock engine or at much different RPM. As it sits in the car, it makes 230-260 horsepower at around 4500 RPM if it is tuned perfectly. You will feel power decrease after that, but will still want to rev past 4500 before you upshift to get the best acceleration.

With the horsepower curve peak at 4500 RPM, you will want to shift around 5000 RPM for optimal acceleration because the engine speed will drop to 4000 RPM or so after the shift is complete. That way, you keep the engine speed sweeping through the power peak as you accelerate. Drag racing 101. 

...also because operation above 5000 RPM is questionable unless your valve train was upgraded and your rotating assembly balanced. Some guys here have engines with power peaks around 6000 RPM so they are shifting around 7000 RPM. They have upgraded their engines mechanically to handle that RPM. Whatever RPM your power peak is at is pretty useless if your engine explodes trying to use it. 

That's with a Holley 600, cast iron intake, free flows, and 2-1/4" exhaust. I'd suspect that your TB is sized for off road work and not higher rpm use and probably a little small then.