Finally a question I can answer! (I'm a mechanical engineer). The relationship between power and torque is described well in the linked article. Here is a cool thing to try, however:

To find your optimal shift points for accelleration, you want to maximize the torque to the rear wheels (meaning you need to take the transmission gearing into account -- to know the actual torque, you also need to consider the final drive gearing and wheel size, but these are constants so they don't change the optimal shift points).

As was mentioned before, to know the exact best shift point, you need to compare rear wheel torque at the engine speed of the current gear with rear wheel torque at the next higher gear. Ideally, that requires a torque vs. RPM graph of the engine.

However, you have two points of the torque vs. RPM curve, because you know the maximum power and torque and the engine speeds where they occur. You also know that the engine develops zero torque at zero speed. So, you really have 3 points of that curve.

It's not perfect, but you can assume straight lines between those three points and come up with a surprisingly good approximation of the ideal shift speeds. To do this, you need to know the transmission gear ratios.

You can write a very simple computer program or use a spreadsheet to compute the transmission output torque as a function of RPM (assuming the linear engine torque curve and multiplying by the correct gear ratios).

When do you shift? Simple. When you get higher torque in the next higher gear. Remember, the next higher gear will be at a lower engine speed.

Using the final drive ratio and the wheel size, you can have your computer program use a vehicle speed increment. I used 1mph in a program I wrote years ago. Wheel circumference x wheel RPM gives you speed, so with the gear ratios and the torque vs. RPM approximation you can express your ideal shift points in terms of MPH. If you do this, you get best results by measuring your drive wheels from the center of the wheel hub to the ground and using that as the radius. The tire is flattened at the bottom, so you want to use the distance from the wheel hub to the ground.

Jim