Mount pump indicators on the unit. The indicators should be mounted on the movable unit, with the dial plunger touching the unmoving part of the unit. Take a reading. These indicators will give you the face, or angular, and rim readings you need to complete the formulae for figuring out the necessary shims.
Measure the diameter at the indicator point of the pump. Measure the length from the indicator point to the first motor support and then from the indicator point to the second motor support. Write down the face indicator reading and the rim indicator reading. These are all the numbers you'll need to figure out the shims required.
Figure out the shims under the first motor support using this formula: L1/D X F + 1/2R. Written out it means: Divide the distance between the indicator point and the first motor support, multiply the result by the face reading and add half the value of the rim indicator reading.
Figure out the shims under the second motor mount using this formula: L2/D X F + 1/2R. Divide the distance between the indicator point and the second motor mount, multiply it by the reading value and add half the value of the rim indicator reading.