This is for myself to remember the shop owner's instruction. Every shop works it differently. Hopefully we could learn more methods from rebuilder friends. The pinblock was fitted to the plate, marked and drilled. Now it is time to trim it to the original size.
On the old/original pinblock, two locator holes were drilled on bass and treble. A paper pattern was made for each side with pencil holes poked on locator holes.
The locator holes were drilled on the new pinblock. Put paper patterns on new block, align locator holes with tooth picks. Scratch the edge of paper with short lines. This will be the edge to cut off. Use a long ruler to connect two ends, mark with pencil. Note the bass edge has an angle. The angle was marked from old block with a line inward. Simply transfer/flip the angle to new block.
Get a reading on the angle from stretcher to keybed using both wixey and angle gage to be sure. Adjust the angle on bandsaw table to match it. The angle shall be as close as possible but don't sweat to make it exact. Draw a line on pinblock 1/8" out side of original edge. Saw on the outside line.
Adjust jointer fence to match stretcher angle, as well. Joint pinblock edge till the inside line/ original edge line just disapears.
Measure bass and treble edge angles with a protractor, adjust chop saw angle to match it. Chop right on or inside the marked line. The block is better a little shorter than the piano case at stretcher. It will allow adjustment from left to right when positioning the plate later on.