When the pressure plate is manufactured or reconditioned, it's balanced as part of the process. Ditto for the flywheel. At the normal RPM range a street engine is likely to run, extra balancing isn't necessary. If you're planning to rev one into the 6K RPM range or above, it might be a good idea to do some more precise balancing, but the engine is going to need some detail work to approach that speed.
Jerry
