"A" is the smallest and "D" is the largest.
I have often thought if you were lucky enough to have a block that was A,A,A,A, you could hone it 4 times with just a torque plate and rebuild it 4 times with stock pistons. Maybe that is too much to ask?
If you are using a NEW/DIFFERENT block, you may need 4 NEW/DIFFERENT pistons to put into the NEW/DIFFERENT block cylinders.
It seems like you should have 6 remaining 'good' pistons between these 2 motors? 1 motor with a piston on the ground, and 1 motor with a beat-up piston leaves 6 good pistons doesn't it?
Are the 2 motors different from each other?
Good Luck!
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