The theory for match balancing is like this:

Take the two flywheels, or flywheel and flexplate, and bolt each one to a flange on the end of a short and straight pipe so that they are 180 degrees apart.

Now, if they are neutral balanced already, when you put this assembly on two straight rails it won't go anywhere. If one or both is not neutral balanced, it will want to roll one way or the other.

What you do in that case is drill holes around the perimeter of the flywheel you are going to use so that the assembly doesn't roll. Beware the "shaving a poodle" effect and drilling holes that are too big. When you get it to stop rolling, the new flywheel is match-balanced to the old.

Ted

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1983 240D automatic, Orient Red, 174K
1983 240D manual, Biscayne Blue, sold at 341K